A diatribe against landscape fabric

In an era of rising eco-consciousness, homeowners are gradually moving away from lawns and other heavily irrigated landscapes.

The trend is toward xeriscapes, landscapes that are designed for climate they are located in, with plants adapted to thrive on little more than rainfall, and gardens that use efficient irrigation systems like drip systems or, in some cases, no irrigation at all. That is definitely a laudable option in my book—when I install gardens, it’s practically the only thing I consider unless I’m asked to do otherwise. Not only is it better for the environment, a site-appropriate garden is more resilient and easier to maintain.

But one unfortunate detour in the path towards xeriscaping is a tendency for installers to plot out gardens with vast swaths of landscape fabric. The material, made of polypropylene plastic, is spun into threads or ribbons and woven into a cloth purported to allow air and water through, then topped with gravel or mulch. The stated purpose of the fabric is to prevent weeds from emerging between the plants, which, in a popular xeriscape style, are placed relatively far apart in holes punched strategically in the fabric.

It’s a no from me

There are a number of low-water garden plants that appear to do ok in landscape fabric, and you have seen them because they are the popular plants to install in road medians and around parking lots, or other rarely-maintained but busy public spaces, where landscape fabric is ubiquitous, or at least has been for a couple decades at the time I am writing this. And indeed, for the first year—or at least at the moment that the installation service collects payment from the property owner—it appears that the fabric is doing its job keeping plants comfortably spaced and blocking the weeds between them.

Many modern xeriscape styles, especially those I see around Denver, seem to exist on the idea of saving water by using a lack of plants. The few that are in place consist of some yucca or a small patch of daylilies, a fernleaf yarrow or two, some sedums, a couple stands of ‘Karl Forster’ ornamental grass, and a big patch of Russian sage, all arranged as islands in a sea of gravely rock. The absence of plant coverage means weeds would have ample opportunity to grow, but are kept at bay, at first, by the fabric beneath them.

That’s not the case the year after. Again, you have seen this before—how often do the gardens around the edges of parking lots keep looking great for long? There are always weeds, and probably a few patches where installed plants have died, and the opening is crammed with cheatgrass because the drip emitter is still trickling water in that spot. Even an untended irrigation ditch or rural highway shoulder, receiving no planting or maintenance whatsoever, probably has prettier vegetation than the berms around a suburban parking lot, middle school yard or boulevard median, where fabric is purportedly keeping things nice. Some lucky properties might get a second or third year out of their fabric, but ultimately, inevitably, the fabric will fail, and the garden will go to chaos unless it’s in an affluent area where it is frequently re-installed.

An example of landscape fabric deteriorating over time with abundant weedy growth on top of it and through it, but desirable garden plants are excluded.

Ironically, a garden bed covered in landscape fabric is like a curated space for noxious weeds

The types of weeds that we have learned to dread most as gardeners are species that have followed human inhabitation around the world—as invasive species, thriving on the peculiar alterations we repeatedly make to land.

Despite the wide variety of weed species we deal with, there are actually some pronounced ecological similarities between the most common garden weeds. They usually resent shade and do not thrive in competition from diverse neighboring plants, but spread eagerly in monocultures like lawns or crop fields or areas cleared by frequent mowing, herbicides, foot traffic or construction. Common weeds are resistant to chemicals that kill other plants, mainly because they have all been sprayed so many times and only the survivors, bearing genetic mutations for resistance, have passed on their seeds. Common weeds dominate dense compacted soils low in oxygen—humans are great at creating these compacted soils along streets, in lawns, in foot-trafficked areas and construction sites—and are tolerant of salt and other common pollutants found in developed areas.

The weeds germinate in two main phases depending on the species—late winter, when nothing else in the garden is active (we don’t often think of this time as meaningful for plant growth, though it is in the wild), or at the onset of hot temperatures in late spring when long days supercharge fast growth. The weeds reach maturity within a few weeks, faster than most other plants do, as a function of the frequently-disturbed settings they are adapted to. They quickly flower and drop more seed, or anchor their roots into deep soil before anything else can displace them.

These weeds—you know them as bindweed, dandelions, thistle, quackgrass, cheatgrass, sorrel and others—are good at overcoming the barrier weed fabric presents to them. They can germinate in the duff layer on top of the fabric and grow in soils that are extremely shallow (such as cheatgrass), or they send their taproots down through the fabric (examples include mallow or curly dock), or they manage to gain foothold under the barrier and spread on long runners that can grow several feet in all directions, searching for an opening. Bindweed and thistle are obvious examples of weeds that advance underground, exploit seams or holes in the fabric, and, left unchecked, can form dense mats on top of it with deep, unreachable roots burrowed in the low-oxygen soils beneath. Meanwhile, desirable plants—many of which can be quite hardy in the face of competition or drought—do not contend well with the surface barrier, and can’t fill in to displace the weeds. Groundcovers are limited to the size of the hole in the fabric that was cut for them, so they more resemble cute miniature plants than the sprawling spreaders they are selected to be.

The above are reasons why landscape fabric doesn’t work as well as we hope it would. But I’d also like to address some ways fabric could be actively harmful, at least in terms of missed opportunity to create a garden with ecological value.

How unnatural barriers block healthy processes in the garden

See, long-lived plants that colonize the soil actually improve it structurally and chemically, to make the soil layers much more porous, absorbent of water and efficient at recycling nutrients. This benefits the plants directly as the soil’s inhabitants, but it also has secondary benefits for the whole system. Plants’ deep roots periodically die and are replaced by new roots, leaving long-lasting channels in the earth, which water can trickle down and oxygen can move through. The leafy and woody debris plants drop on the soil surface feeds microbes that bind silt and clay particles to bits of organic material, forming granules that give soil a grainy, light texture even if the inorganic components are otherwise very fine and sticky. The worms and burrowing insects that feed off of dead leaves and roots stir the soil and make larger channels, crossing the soil profile in many directions.

All of this activity, in aggregate, drags organic material—often referred to in shorthand as carbon—deep into the soil, where it is sequestered for many years, and helps draw heavy rainfall into the deep layers, and also gradually wicks deep water back up towards the surface when the top layers are dry.

All of this further serves to capture heavy rain and hold it on site, or gradually feed water to aquifers, with minimal runoff. Limiting runoff has the obvious effect of reducing flooding, but also means our urban pollutants (mostly nitrates and sulfates) can be processed by soil bacteria and rendered harmless before they reach natural waterways. When land is covered by deep, porous, biologically active soil, streams are fed by rainwater moving through soil over weeks rather than runoff pouring over the land in hours, and thus streams will not swell as intensely in storms or dry to a trickle during brief droughts. Deep, uninterrupted soils also mean that water stays put in deep layers of soil for a long time, and plants can draw from the reserves between rains, so there is less need for irrigation, less loss of plant life during dry spells, and more biological productivity on the whole.

Landscape fabric interferes with all of this. When soil particles mesh with the fabric, it forms a sheet that is far less permeable to water and oxygen than the fabric initially was. Between holes punched in the fabric for plants, the soil surface is relatively lifeless and hard, although lifting a sheet of fabric might reveal the thin, white etiolated stolons of bindweed and Canada thistle corkscrewing in all directions just beneath it.

The benefits of open, mulched soil with no barriers extends to animal life as well. Beneficial insects—both carnivores, which eat other insects, and detritrivores, which eat dead leaves, stems and fungi—overwinter below ground and benefit from free movement between soil and the sky. Small birds, in turn, rely on an abundant supply of earthworms, beetles, grubs and arachnids in the mulch layer. This supply of protein is crucially important for them raise their young, as you will see when they arrive to pick through the garden and burrow into the duff layer with their heads. Soil creatures will also come up to eat dead plant material or to drag it into their burrows to moisten it so they can eat portions as they decay, cleaning up the garden and recycling the nutrients. All of this life and activity depends on a barrier-free continuum between the sky and the soil—two realms that are not really as separate on Earth as they seem.

Another example of weedy growth on landscape fabric. The fabric needs to be removed before the garden can be cleared and replanted, which is all the more difficult when it is buried under decayed organic material and grown over by plants, while the soil remains compact beneath it.

With this, I hope it’s clear that landscape fabric can cause more problems than it solves. A relatively recent invention, landscape fabric is a strategy that, though logically understandable, doesn’t hold up in practice—like so many of our attempts at micro-managing nature. Instead, using organic mulches like wood chips, or other natural materials such as large stones, can change the structure of a perennial garden favoring desirable plants over opportunistic weeds. In turn, it allows the plants themselves to control their habitat, feeding wildlife and forming a garden that does not deteriorate with time, but grows only more well-established and resilient.

Why snow cover is good for your garden

For those in northern latitudes, winter is a slow time in the garden. Plants are dormant, nursery stores are bare, and for most of the winter it’s still too soon to start your seed trays for the vegetable garden.

But one thing that keeps me active through the winter months is taking advantage of snow. In Denver, a semi-arid region in the rain shadow of the Rocky Mountains, we rarely if ever get deep accumulations. Six inches is a big storm, twelve is massive. It usually melts completely before the next snow. That’s to be expected in a climate with between 10 and 15 inches of precipitation in an entire year. But when the snow comes, I’m ready, heading out to scoop the treasure and pile it in the garden.

How snow protects plants from cold

It’s counter-intuitive that something that is, by definition, frozen, helps protect the garden from winter’s dramatic temperature swings. It comes down to the ways that plants protect their dormant tissues from the destructive power of ice.

Dehydration as protection

Plant cells are mostly water, and for non-adapted plants, ice crystals forming in cells pierce and rupture them. When the plant thaws, the pulverized tissues hang limp like cooked spinach, utterly destroyed.

Cold-adapted plants have a variety of defenses. First and foremost, they prepare for cold by allowing their tissues to dehydrate. They will often do this by moving cellular water to the spaces between cells, where it can freeze safely. Inside the cells, the water becomes thick and syrupy with sugar, electrolytes, peptides and enzymes that interfere with ice crystallization. Instead of freezing at 32 degrees Fahrenheit (0 degrees Celcius) as pure water does, ice in plant cells may not form until the temperature drops to 25 degrees, 20 degrees or lower. (The limit depends on the species, the variety, and how much time the plant has had to prepare for coming frost.) As temperatures continue to drop, more water will migrate outside the cell and freeze, leaving the inside even more dehydrated. Thus, freeze tolerance in many species goes hand in hand with the plant’s ability to cope with drying out.

Eventually, temperatures drop low enough that cell contents freeze, which is lethal to tissues on plants that die to the ground each winter. Those with perennial above-ground tissues may tolerate ice inside the cell. (Cell contents are by now so dehydrated that there’s only so much damage ice crystals can do.) Other kinds of plants retreat to the ground, where the thermal mass of the Earth keeps roots and storage organs within tolerable temperature ranges.

The burdens of sun and wind

Yet, even when plants are able to survive a frozen-solid state, they have additional issues to contend with. Drying winds and sun can loosen frozen water molecules and convert them directly to vapor in a process called sublimation. (Though very tough plants can survive down to 25 or 30 percent water in their tissues, they cannot survive drying out completely.) Oxidation reactions with air can degrade tissues when the frozen plants are unable to produce antioxidant compounds to protect themselves. Ultraviolet light from the sun damages cell organs and DNA. During the growing season, plants are constantly repairing damage from these assaults. But plants can’t heal while frozen, and damage accumulates. Thus it is not just the winter’s minimum temperature but also the length and frequency of hard freezes that determines whether plant tissues are injured beyond a point of no return before spring.

Snow creates a stable, protected environment

Fortunately, most of these issues are ameliorated by snow. Because a layer of snow is mostly air—around 95 percent air after a fresh, fluffy snowfall, and at least 80 percent on old, crusty snow or heavy wet snow—it is an excellent insulator. As temperatures crash below zero outside, they stabilize at around 25 degrees Fahrenheit when measured 4 inches into the snowbank.

Next, snow blocks ultraviolet light, and keeps stems and leaves from drying in a zone of 100 percent relative humidity. Yet despite the moisture, oxygen can diffuse through and most pathogens cannot grow below freezing. Thus, snow cover can keep even fairly tender plant tissues in a state of happy, mostly suspended animation for months on end.

A few bonus benefits of shoveling your sidewalk snow onto the garden

In the Western U.S. we’ve been contending with a gradual drying trend and droughts that get more severe with climate change. At the same time, though temperatures have gotten on average warmer, they also swing more fiercely now. Sudden spring cold snaps injure plants more badly when they’d let down their defenses during a warm spell.

Snow cover helps with both these problems—keeping plants properly chilled through winter, and supplying extra moisture that is happily taken up in spring.

An additional bonus for me is that it protects the environment. Runoff from streets in winter carries pollutants such as sidewalk salts (magnesium, calcium or sodium), fertilizer, oils, nitrates and sulfates. Often, stormwater systems move runoff directly into lakes, rivers and streams. When these substances contact soil, they’re quickly scooped up by soil microbes that convert them into nutrients. Those nutrients are in turn taken up by plants. But urban runoff systems don’t often exploit that step, sending water directly into streams. There, the pollutants are far more harmful, since they interfere with aquatic organisms’ ability to use dissolved oxygen. Thus, I’m helping clean the streets at the same time I protect and fertilize my garden.

Do trees die of old age?

Everything in nature dies. Human beings can live close to a century, but few do, and no one has lived past 122. Dogs live on average 8 to 14 years. Some tortoises can live to be 200. In vertebrates, changes on the cellular level give animals an upper limit on lifespan. Cells can only divide so many times before they’re compromised, making older individuals much more frail and vulnerable than youthful individuals.

Plants are fundamentally different: the larger and more established plants are, the higher their survival odds become. Out of 1,000 seedlings, only one may live to become a tree. But once a specimen is mature, it can be extremely resilient. Many common trees have potential lifespans in the centuries, towering over rivals and growing stronger every year.

Despite this trajectory, it’s uncommon to see single-stemmed trees grow past a thousand years old. So what limits them?

This is one of those questions I love, because there are so many angles to understand it from.

A tree is a system of redundancies

Unlike vertebrates, plant cells do not age. A rooted cutting from an ancient tree is identical, on the cellular level, to a young plant.

In fact, even in old trees, the live cells—leaves, roots and cambium—are young. Old leaves fall off, and new leaves grow. Feeder roots—the thin, water-absorbing tips and branches of the robust structural roots—also die and regrow cyclically, the same way leaves do.

The xylem—the tubes that carry water and minerals up a tree—are already dead. These cells are the most important type of tissue in determining what makes a tree a tree. Xylem cells form cylinders and die as soon as they mature, becoming conduits for fluid. Because they’re dead, xylem tubes cannot self-repair. Within a few years they develop tears and air pockets that stop them from working, so new cells replace them. At their final stage, defunct xylem cells are the wood. They are the old growth rings on the inside of the tree, existing only to hold it up. Their replacements, new xylem tubes, continually form on the outside of the trunk’s circumference, as new growth rings.

Phloem cells—which transport hormones and sugars from the foliage to the roots—also die annually. Unlike xylem, they are soft and rubbery, not rigid. They are also still living when they do their work. When spent, they die and collapse to a fraction of their former size, and are ultimately pushed outward as bark.

Between the phloem and xylem is a thin ring of tissue—the secondary meristem—which originates all the structural cells. It is rapidly dividing, and cells there migrate in to become xylem and eventually wood, or outward to become phloem and eventually bark.

Thus, all tissues in a tree are constantly turning over. The tree is less like a body, and more of a system. A tree’s young living layer clings to the skeleton of its own dead xylem, like a modern city on ancient ruins, or the live surface of a coral reef. All the while, it is growing in size. With time the system progresses through a structural evolution that defines the stages in its life cycle.

One mechanism that gives trees more resilience is redundancy. Remove a branch, and the loss of its hormone signal will resonate through the rest of the tree. Other branches grow more vigorously to correct for the loss, restoring the ratio between roots and shoots. If a fire or animal damages the vascular cambium on one side of a tree trunk, the cambium on the other side of the tree will thicken to compensate. Meanwhile, cells around the edges of the wound will grow inward to hopefully seal it off.

The hormone signals plant parts send throughout the plant are the only way a twig has any awareness, so to speak, as to whether it is a lower branch on a big tree, or a seedling on a forest floor. Aside from environmental stimuli—light, water, temperature and nutrients—hormones control how different sections of a tree cooperate. For example, if you remove a twig and root it, the hormone signals it receives will change. It is now much closer to cytokinin-producing roots and not getting suppressing auxins from higher foliage. In response, it will begin growing more vigorously, taking on characteristics of a seedling.

Now with that background info out of the way I can get more directly to the question: if the tissue in the tree does not age, and it continuously resets its behavior based on ongoing hormonal cues, why don’t trees live forever?

The problem is the accumulation of defects, which, over time, can overwhelm repair processes. The tree eventually reaches a point where it is much more difficult to keep things working properly.

Plants do not have cellular aging, but old trees suffer structural defects

• First: bigger trees usually have a higher ratio of unproductive (non-photosynthesizing) tissue compared to productive tissue (foliage). A seedling has leaves, a short stem, and roots. In a big tree, the leaves and branches are much higher and farther from the root tips. That means there is a long span of vascular tissue that must be kept alive. Trees expand their canopy as they grow, but the ratio between the massive cambium covering the trunk and branches, and the finite horizontal surface area determining the canopy’s access to sunlight, increases. The vascular cambium needs to maintain complete coverage over the heartwood to protect it from decay. Over time, there’s less energy to invest in new growth, so bigger, older trees grow more slowly. They’re also less able to correct structural defects like wounds.

• As a tree grows, the redundant parts communicate using hormone signals to work as a cohesive whole. Genetics, size and environmental stressors determine the size and circumstances in which the tree transitions to its mature stage. Gradually it uses resources to produce flowers, fruit, and seeds, investing less in growth. Some long-lived species may also invest more in energy storage when they get big, slowing growth further.

• The most important limit on the lifespan of old trees is decay in the heartwood. Even healthy middle-aged trees have a few pockets of decay here and there, but the tree’s ability to add new wood each year keeps pace so the tree remains strong. In very old, very massive trees, it is more difficult to defend a vast surface area, especially when decay pockets begin to coalesce inside the tree.

(One of the limits on the size and age of douglas firs, a very big and long-lived tree, is the fact that virtually all wild trees live with a decay fungus called dyer’s polypore. The fungi grows slowy, and the trees can be ancient before they eventually fall, so it’s not harmful to the species as a whole. But theoretically, if the polypore were not there, doug firs might be able to outgrow redwoods).

• In natural settings, competition limits the lifespan of old trees. Size provides incredible advantages reaching light and absorbing water, but there’s a point when the benefits max out. A big tree doesn’t have the opportunity to shrink its tissues to a more manageable size in a drought or disaster without exposing its dead heartwood to the environment and decay. Any loss of canopy requires a corresponding loss of roots, allowing other plants and trees to colonize soil and challenge the old tree’s dominance. Ancient trees tend to develop large sections of exposed, decaying heartwood, which means big portions will eventually break off. This means they often lose their tops, resprouting foliage from lower down. That costs them the advantage of height, while they still face the burdens of high tissue mass and very large sections of exposed heartwood that lead to continued breakage. An ancient tree may go through multiple cycles of breakage or dieback and regrowth. Each time, it accumulates a greater burden of decay, since the cambium is less and less of an intact cylinder covering the structure. Eventually, trees cannot compete against their less burdened neighbors, and die off while middle-aged trees assume dominance.

One other thing, more speculative on my part: plants get viruses, and viruses are not curable in plants. Usually, the plant continues to live, but less vigorously. Many plant viruses are asymptomatic, and their only effect is a metabolic burden leading to more stress and less growth. Luckily, most plant viruses do not get passed on to seeds. So there may be a point when the viral burden is high enough that the old tree is struggling too much and a seedling tree would be much better off. However, there would have to be more study into old trees and the presence of asymptomatic viruses for me to decide whether this is a realistic factor.

Why are there so many dying trees? What emerald ash borer damage looks like and what we learn from it

If you follow news about trees and gardening, you’ve probably been hearing for many years the ominous news of a devastating invasive insect called the emerald ash borer.

The emerald ash borer, a shiny green beetle destroying ash trees across North America, emerges fron a D-shaped burrow in ash tree trunks in early spring.

History of the emerald ash borer in North America

Ash trees are—or were—one of the most common tree types in North America. Our native ash species include green ash, black ash, white ash and a few others, with extensive natural ranges as one of the most dominant tree caregories in the eastern U.S. They’re also popular in yards for their dense shade and tolerance against late cold snaps, summer heat, periodic drought, and soil compaction found in developed areas or under pavement.

Ash trees, a genus with many species, grow wild across an extensive range spanning North America, particularly in the eastern part of the continent. Additionally, ash trees are one of the most common trees planted in urban areas.

In addition to the North American ash species, there are other ash tree species found around the world, including northwestern Asia where ash trees have contended with the emerald ash borer for millennia. The trees co-evolved with the beetles, making the trees resistant to severe infestation just as the beetles became completely dependent on the ash trees to complete their life cycle.

The pill-shaped, iridescent green flying beetle lays its eggs on bark. The larvae burrow beneath to feed on the carbohydrate-rich cambium layer, the green living tissue just under the bark that lays down new growth rings each year and carries sugars from leaves to roots.

After growing beneath the bark until fall, emerald ash borer grubs pupate through winter and emerge as beetles to infest other ash trees. When a beetle finds a fitting ash tree host, it produces pheromones to attract many others to come in, overwhelming the tree’s ability to drown them out with sticky sap.

In ash trees with no resistance to the emerald ash borer, the larvae burrow so extensively under the bark that they completely cut off the flow of carbohydrates through the vascular system to the roots.

Asian ash trees have long adapted to the presence of the borer; North American trees have their own species of slower-growing borers that can damage but rarely kill the trees. Asian ash trees survive infestation from the more aggressive borer species by producing chemicals that slow the insects’ digestion and thus slow their growth, among other adaptations. That way, they can create new tissue faster than the borers eat it, and achieve a healthy equilibrium with the beetles.

North American ash trees have no resistance to the Asian beetles, so when the first infestation was discovered in Michigan in 2002, it set off sirens for ecologists concerned about the future of several vitally important tree species.

The borer population exploded. Within years, ash tree forests across the Midwest and eastern Canada were wiped out. Entire pure stands of ash were converted into shrubby meadows, with ominous dead gray trunks standing over them, as if a wildfire had burned through. Shortly after, mixed forests lost their ash tree stocks. Traveling a few miles per year, the borers spread throughout the region, and occasionally hitchhiked on firewood or other human transport to arrive in other portions of the continent.

Ash borers invading the continent have resulted in vast swaths of dead forests in the Eastern U.S. and Canada.

Infestations in Boulder County, Colorado began several years ago, initiating a government quarantine against ash wood products being moved from Boulder to Denver or beyond. But when the borers were identified in the northern Denver suburbs in 2019, the quarantine was retired since there was now no way to stop them from flying tree to tree and infiltrating the entire metro area.

The documented extent of emerald ash borers in North America as of summer 2020.

In 2021, this is the first summer we’ve seen extensive damage to virtually all of the untreated ash trees in the region. While it’s uncommon to see adult beetles, the signs are impossible to miss.

How ash borers kill ash trees, and how to identify the damage

Emerald ash borers destroy the part of the tree that carries sugar from the leaves down to the roots (the outer layer of cambium or phloem), but they do not stop water from rising from the roots to the leaves, which travels through nonliving tissue (xylem) in the inner cambium. Because the xylem carries only water and minerals, it doesn’t have the carbohydrates borers need to grow and the grubs won’t eat it. That means that the tree can produce leaves for a while even after the infestation is advanced.

But without phloem to carry sugars made in the leaves down to the roots, the entire root system begins starving. It is unable to produce an adequate number of annual feeder roots that sprout from the larger woody roots. Unlike other tree diseases that may kill a section of the canopy at a time, the entire tree’s system for staying alive begins to fail. The appearance is similar to a tree that has a girdling root, or is being girdled by a grate or has experienced other extensive damage to the roots: the canopy thins from the top down and starts retreating.

An ash tree with an advanced ash borer infestation has already suffered extensive damage to roots, starved because the insects have cut their supply of energy from leaves. The canopy, in turn, dies back from the top to try to achieve a more manageable size. It happens on all branches at the same time rather than in sections, which would be a sign of a different kind of pathogen.

During the first season, an ash borer infestation can go completely unnoticed. The first subtle sign is either woodpeckers showing an unusual interest in the tree or small, D-shaped holes in the bark where the first generation of beetles hatched out to mate and lay more eggs.

Trees that are already catastrophically damaged by ash borer can continue to produce dwindling leaves for a year or two because the part of the circulatory system that carries water—located deeper in non-living wood—is still intact. But there’s no hormone communication between the roots and leaves, and no sugar making its way down to feed the roots. Soon, the roots die back and reduce their ability to absorb enough water for the whole tree at its current size.

A tree with inadequate roots, no matter the cause, thins out at the top (which is the the most distant point for water and hormones produced by roots to reach). Trees cope with severe root loss by trying to restructure themselves: they sacrifice leaves and branches that are no longer getting enough water and nutrients to photosynthesize, which starts at the top. Ash trees will produce new green shoots from large branches or trunk, and the new growths can be very vigorous and dense. However, their vigor is deceptive since the total number of leaves is much lower. This would effectively make a smaller tree, which in some scenarios would return to balance with the weakened root system and allow the canopy to regenerate, albeit with a very poor branch structure.

Unfortunately, in the case of an ash borer infestation, these attempts at restructuring the canopy are futile—the root system is not going to rebound since it has been separated from the canopy by ash borer tunnels. The root system is already dying by the time the top level of branches is completely bare.

Usually, the severe damage becomes obvious in late spring when higher portions of an ash tree will fail to leaf out or the tender new leaves die off shortly thereafter. You don’t see much progression in the middle of the growing season since the dying roots can continue to provide a limited water supply to lower leaves. Meanwhile, chunks of bark may begin to curl back or fall off since there’s nothing attaching them to the underlying wood.

You also don’t see much severe wilting and browning in the canopy from ash borer. Browning and singing of the leaves, which occurs, for example, in apple and pear trees affected by diseases like fire blight, suggests a cause that is affecting the ability for water to reach the leaves through xylem. Xylem exist below the upper cambium in channels made of columns of cells that have died and become like hollow straws (the wood’s grain). Bacteria or fungal diseases exist as single cells or filaments that are one cell wide, so they can grow right into the water-carrying xylem channels and shut them off. Infected twigs and branches wilt and turn brown in days.

But because the xylem on infested ash trees are still intact, leaves stay hydrated and don’t yellow or wilt dramatically. Yet, the tree, sensing a nonproductive branch, eventually cuts off the water supply to limbs and retreats further down toward its base.

Later stages of ash borer infestation in a tree

Even green shoots from the base of a mature ash tree infected by emerald ash borer will eventually die as the root system dies, but younger trees, or trees that produce shoots through the soil itself, can form permanent shrubby base growth as they die. The ash borers eventually leave and move on, since they only eat living trunk tissue, and only lay eggs on trunks and branches that are more than a few inches thick.

In trees with basal shoot growth that outlives the dying tree, it’s due to new root systems emerging from the base of each green shoot where they contact moist soil. These bushy, limited growths are vulnerable to drought until the roots grow larger, and they won’t be useful as shade trees. They will only be infested again if they reach a substantial size.

In the last phase of an ash borer infestation, the borers may move on since the part of the trunk they eat is now dead. The tree will produce new shoots from the base, but even these will continue to decline since the root system is so severely starved.

Mature, valuable trees can be protected with systemic insecticides applied before or early in the infestation. But trees that are completely girdled by borers are too far gone even if they still have living portions of canopy, since the roots are dying. Arborists can make a judgment call as to whether the tree is salvageable, usually deeming trees to be too far into the process if the top of the canopy has lost 50 percent or more of a healthy density of leaves.

Asian ash tree species, or hybrids between North American and Asian species, may have enough resistance to ash borers to survive after the first big wave of infestation has passed through a region. Horticulturalists and ecologists are already working hard to develop new ash tree stocks that can resist the borers and potentially restore some of the ash tree options for urban trees. They may even be able to develop strains of native trees to reseed American forests.

Lessons from the emerald ash borer

We as gardeners and tree lovers can take a few valuable lessons from this slow-moving disaster. First and foremost, we need to be conscious of the threat of invasive species. This is not the first time a wave of disease or pest insects threatens to wipe out a major class of North American trees, and since other types of tree epidemics are still making their way around the continent we know it won’t be the last.

Better inspections of plants coming into the U.S. can help, and by carefully observing the environment around us, we may be able to notice, slow down, or eradicate ecological threats before they become unstoppable. County extension offices, which are local branches of state agricultural universities that exist to communicate with the public about landscape health, can be a resource to funnel information to the attention of trained scientists.

A second lesson is to encourage a broader diversity of trees and plants in our urban landscapes. In the recent past, Denver’s urban canopy was dominated by a handful of tree species or families. A loss of one species means a loss of a huge portion of the mature urban canopy, leaving tremendous gaps that take decades to fill with newly-planted trees. By recruiting new species into cultivation (particularly natives in the region), and making sure that each park, yard or city block has several types of trees in it, we can hedge against the chance that a future tree epidemic leaves huge portions of the city bare.

Finally, we can be conscious of the benefits of inviting a diverse array of wildlife into our spaces. Although pests like the ash borer are sometimes unstoppable, they do have natural predators here: woodpeckers, with many native species in this area, eagerly eat emerald ash borer larvae and have actually grown in population in places where the ash borers provide a generous food supply for raising chicks. Other microbes, insects and birds can help compete against current and future destructive pests as long as they have a large enough base population to respond quickly to a major change.

By planting diverse seed-producing gardens, tolerating a moderate amount of native insect pests providing steady food sources, converting rooftops, pavement and gravel strips to open landscapes with lots of region-appropriate plant species, and limiting the use of chemical controls to occasional spot-treatments only, we can create a balanced, abundant urban ecosystem that provides shade and beauty to humans and animals alike, for generations to come.

The meadow garden: where change takes center stage

A meadow garden inverts our common sense of gardening. Instead of cleaning up and simplifying an area, the meadow garden deliberately mimics nature. Instead of arranging plants in grids and rows, the meadow lets them escape and spread. The meadow garden focuses on texture and movement, and is encouraged to change throughout the seasons or the years.

A typical yard has rows or patches of flowers and shrubs around its centerpiece, the lawn. In the meadow garden, it’s the walkways and hardscape that provide structure—as a winding path of cobblestones, a rectangular strip of crushed granite, or a patio. The designer is invited to envision, first, the most appealing way to move through the space. You think about where you’d like to stop or sit, where you’d like to create a focal point, where you want to place a birdhouse or some boulders. The plants cover the remaining area—they are the negative space. In that sense, instead of focusing on the appearance of a garden, a meadow garden focuses on how you will spend time there.

Of course a meadow garden offers many practical rewards as well. Once established it’s very low-maintenance—spreading, rhizomatous or reseeding plants crowd out weeds. Dead stems and flowers provide interesting shapes through the winter so you don’t need to constantly cut things back. The garden provides food for birds and wildlife, hosts a variety of native plants, can be made to require less irrigation, and mulches itself with its falling leaves and stems, gradually improving soil. That might be why this is an increasingly popular garden style for both high-budget public gardens and cost-conscious home gardeners alike.

What is a meadow garden?

Although there is no explicit definition of a meadow garden, meadow gardens typically have the following attributes:

  • Usually covers a larger area than a border garden
  • Grows in full sun to part sun
  • Can be installed with small plants (plugs) and seed, saving costs
  • Makes use of natural rainfall with low to moderate supplemental water
  • Emphasizes grasses, artemisias and textural plants rather than blooming flowers alone
  • Is structured around grassland perennials, plus some annuals that self-seed on their own
  • Tolerates dead flowers, cones and seed pods for visual interests rather than clearing them immediately—a true four-seasons garden
  • Includes plants that are native to the region
  • Considers the plants’ usefulness to birds, wildlife and pollinators
  • Incorporates spreading plants that spread into each other rather than leaving gaps

Creating a meadow garden

Since meadow gardens tend to cover a large area, there are both benefits and challenges. One benefit is that it is more affordable to fill a large space with rapidly-spreading perennials than to do so with slow-growing specimen plants. On the other hand, meadow gardens defy the familiar residential yard structure and require well-placed paths and boundaries to contrast the chaotic nature of the planting beds. Figuring out how to design them well and prepare such a large space for planting can be intimidating.

Planning/designing the garden

Start planning a meadow garden by identifying inhabitable spaces within the garden’s boundaries. If you’d like to include a sitting area, water feature, designated spot for bird feeders, a gazebo or deck, designate those spaces first. Your vision for large shrubs and trees should also come before garden beds. Plant structure and growth in full shade are vastly different and fall under the category of a woodland garden rather than meadow.

  • First step: The borders of the meadow garden are ascertained (in this case the whole yard) and the flagstone patio, seating and fire pit are planned. A winding path is drawn. Solid dark dots represent sprinkler heads in a sprinkler irrigation system.
  • The first order of plants—the tallest flowers and grasses—are designated first. They fill mostly central areas. In most cases, tall plants won’t be close to sprinkler heads where they can block irrigation to other plants.
  • After the largest plants are mapped, shorter plants and spreading plants are plotted, careful to place contrasting shapes and textures side by side.
A hypothetical meadow garden planned in three stages: first hardscape (seating area, trails), then large anchor plants, then smaller fill plants. After that, seed can optionally be sewn over various sections of the garden and additional planting will fill any gaps that materialize.

After you’ve identified your garden’s access points, such as patios or benches, sketch out the walkways between them. Paths can curve, cross or meander, depending on your preference. Straight, square-edged concrete walkways can make an attractive contrast against the billowing drifts of plants, but a crushed stone path that follows a winding arc with flowers and grass spilling over the edge can be beautiful too. It’s also wise to create some narrower, lower-order walkways to divide up large planting beds, for both aesthetic and practical reasons. The secondary paths help you move through the garden without trampling plants, and allow you to enjoy them from different vantage points.

Then, it’s time to figure out the plan for plants. Start by plotting zones for tall, medium and short plants. Site taller plants in the center of planting beds, away from walkways, while shorter plants will line the walkways. Be mindful of views you want to preserve or eyesores you want to screen from various vantage points. Also be mindful of sprinklers: if you have an automatic irrigation system, avoid blocking spray nozzles with tall plants.

Think of flower colors and textures you want to design with. I think it’s best to pick two to three core flower colors per blooming season in a section of the garden and select plants that blooming with various shades of those colors. A few off-theme accent plants can be OK, but sticking to a core color palette will create a much more harmonious and professional look. Arrange large swaths or drifts of many plants of the same species, scaled to the overall garden size. (Enormous gardens may have swaths of tens to hundreds of plants of the same species together, while smallish gardens might only have room for clusters of 2-3 plants). Try to put contrasting textures near each other: grasses next to broad-leafed plants and flowers, plants with sprays of small flowers near plants with large flowers, and plants with silver or purplish leaves beside plants with unremarkable green foliage, and so forth. Consider repeating patterns, with the same species appearing in drifts or clusters in multiple places in the garden rather than a single section for each type of plant.

Clearing the space

What’s the best way to eradicate weeds or lawns to begin planting a garden? Do you need herbicide? Do you need to solarize?Should you till everything up to prepare the soil? I find that less intervention is often quicker and more reasonable: simply covering lawns and weedy areas with a 1/2 to 1-inch layer of compost and then few more inches of cheap, bulk wood chip mulch can smother the grass and create a fertile expanse for a meadow garden to go in.

This meadow garden is being installed in Westminster, Colorado by expanding existing garden beds over a lawn area. I spread a crushed rock path and thin compost layer directly over turf, which, in addition to a 3 inch mulch layer, is sufficient to block sunlight and kill the lawn and weeds. It is immediately ready for plants, as long as grass is removed directly under the plant since the mulch will be parted there. Spring 2020.

If mulching is generally good for gardens, why does covering a lawn or weeds with soil and wood chips kill it?

Simply covering unwanted plants with wood chip mulch can be a surprisingly effective way to weaken and kill them. (Woody shrubs, bindweed, quackgrass, Canada thistle and invasive groundcovers like vinca may be an exception.) Don’t chop the stems off, simply trample them down and cover. Although dormant plants can push spring shoots through mulch and soil to reach sunlight, unwanted plants buried intact during their vegetative phase are often unable to do this. Generating new shoots is a hormonally-driven process in plants—it occurs when there is a loss or absence of existing stems and foliage. Since the weeds and lawn grass still has its vegetation under the mulch—making hormones that signal that the plant still has stems and doesn’t need to create new shoots—weeds wait for daylight that doesn’t come, and exhaust stored energy trying to grow more leaves under the covering.

In most cases, some bits of growth will manage to reach the surface, but they will be weakened, easy to pluck or cover again to deplete them further. Desired plants, on the other hand, have been taking advantage of the fertile season and are prepared to shade and out-compete residual weeds. Occasional light weeding, when vigorous garden plants are becoming established, is enough to tip the balance of power away from weeds and eradicate the majority of them.

In this image I started the process of planting the meadow garden while the lawn was still being covered in compost and mulch. I sacrificed a single, mature Salvia pratensis plant by bare-rooting it and stripping the fibrous main stem into 26 divisions, each with some top growth and connected roots. They were planted directly into the ground under the compost on both sides of the path. 25 of the 26 survived. Spring 2020.

Trails and paths made of crushed stone or sand and flagstone can go right over the weeds and turf as well. (For flagstone or flat pavers, it is better to mow the weeds close to the ground so that the stones don’t shift as the smothered plants decay.)

Just be sure to plant new plants directly in the native soil rather than the pure compost, which will burn tender roots. After a season or two, the compost will break down and merge with the underlying soil.

In this alternate view of the same Westminster, Colorado garden, the lawn is immediately transformed into a clean slate for planting with a top-dressing of compost and mulch. Some of the larger plants had already been growing in the previous garden bed and kept in the new plan. But if you look closely you can see dozens of perennial divisions planted in the area, at very low cost because they were propagated from a handful of fast-growing perennial plants. Spring 2020.

A note on tilling

Tilling is a popular way to clear a garden plot for planting and many guides recommend it as a way to clear beds and “soften” soil for roots. I dispute that. The most aggressive resprouting weeds will return from roots. Soil with existing grass, weeds or other plants is going to be full of beneficial channels where roots have grown and died, worms and burrowing insects have cleared tunnels, and microscopic fungi have built soft fibrous bands of tissue to move water and nutrients around. The existing porosity will allow water to quickly soak into the soil, and new plants’ roots will follow the channels left by old roots to grow deeper more quickly than in compacted soil.

Tilling tends to collapse the soil’s structure. When tilled soil gets wetted again, it becomes muddy and dense. Beyond that, tilling is extra work!

When I plant a small plant or plug, I’ll break up the soil a few inches around the planting hole to remove existing weed roots and make sure soil fines are able to dissolve and settle around the new plant’s roots, but I do not till a broad area. Similarly, when planting seeds, I disrupt the top inch or so of soil to clear competing plants, but don’t go any deeper than that.

This garden is in a residential front yard in Broomfield, Colorado. The homeowner seeded part of the yard with a wildflower and drought-tolerant grass seed mix a few months before I came in to install a more formal meadow garden. After laying crushed stone paths, I began adding yarrow, sedum and lamb’s ear by breaking up the soil in a 12-inch-diameter patch around each new plant so it can establish without competition, and then covered the root zone with mulch. However, some of the grass and flowers can be allowed remain in the gaps to add to this garden.

Planting the garden

A garden doesn’t need to be complete all at once—they take time to mature, and you may be discovering new types of plants you’d like to add in for years to come. But the first plants to install are your big, fast-growing, spreading and reseeding plants, because they will help fill the space, out-compete new or remaining weeds that sprout and give you an immediate reward. You might also be comfortable with letting an aggressive plant, such as lamb’s ear, yarrow or milkweed, spread widely at first, and eventually clear patches of it add new types of plants.

Back in the Westminster garden, young plants are quickly getting established a few months after the original bed was expanded.

Using the same process I used to divide a single Salvia plant into many new plants, I added many other drifts of small plants by splitting up larger plants that had been planted in a nearby garden 1 year earlier. That included fernleaf yarrow (one plant made 15), Stella d’Oro daylilly (one clump made dozens of small clusters around the path edges), lamb’s ear (one clump made a dozen), Rocky Mountain Penstemon (one plant made 15), variegated maidenhair grass (a portion of an old clump made 7), indiangrass (1 clump made 5), little bluestem grass (1 clump made 5), Artemesia ludoviciana (as basal stem cuttings from several plants) and bearded iris (several nearby clusters were divided). There are also 5 nursery-purchased butterfly weed plants, 1 nursery-purchased false indigo, and 3 nursery-purchased anise hyssop. The pink daylilies, Russian sage and foxtail lily seen here going to seed were already established here.

Because of the cost-savings of using very small divisions of fast-growing plants, the total installation costs included less than $200 of raw materials and new plants. Although existing plants to propagate aren’t often available, the small starts can be seen as the equivalent of using very small plants or plugs from a nursery. Summer 2020.

Fast-growing, tall/large meadow garden plants include:

  • Large ornamental bunchgrasses such as maiden hair grass (Miscanthus), indiangrass (Sorghastrum nutans), big bluestem (Andropogon gerardii), switchgrass (panicum), feather reed grass (Calamagrostis varieties), giant sacaton (Sporobolus wrightii), pink hair grass (Muhlenbergia capillaris) and ravennagrass (Saccharum ravennae). Some of these get very large so be sure to read the description.
  • Fernleaf yarrow (Achillea filipendulina)
  • Russian sage (Perovskia atriplicifolia)
  • Maximillian’s sunflower (Helianthus maximilanii)
  • Artemisia ‘Powis Castle’ (Artemisia hybrid)
  • Showy milkweed (Asclepias speciosa)
  • Goldenrod (Solidago)
  • Joe Pye weed (Eutrochium purpureum)
  • False indigo (Baptisia australis)

Additionally, a meadow garden needs variations in height with many shorter species as well. Often, the best medium-sized perennials are those that will spread, multiply and/or reseed.

Second-order plants to quickly fill a meadow garden:

  • Medium-sized ornamental grasses including fountaingrass (Pennesitum), little bluestem (Schizachyrium scoparium), blue grama grass ‘Blonde Ambition’ (Bouteloua gracillis), as well as spreading or running grasses such as blue lyme grass (Leymus arenarius) or ribbon grass (Phelarus arundinacea). Be cautious with the spreading grasses, some may overtake non-aggressive plants.
  • Prairie sage (Artemesia ludoviciana)
  • Yarrow (Achillea milefolium)
  • Meadow sage (Salvia nemorosa)
  • Rocky mountain penstemon (Penstemon strictus)
  • Lupines (various species, Lupinus)
  • Lamb’s ear (Stachy’s byzantium)
  • Butterfly weed (Asclepias tuberosa)
  • Jupiter’s beard (Ceranthus ruber)
  • Bearded iris (Iris germanica)
  • Siberian iris (Iris siberica)
  • Black-eyed Susan (Rudbekia hirta)
  • Purple coneflower (Ecinacea sp)
  • Globe thistle (Echinops rito)

Another way to quickly conquer space in a new meadow garden is by scattering seed around the perennial starts. Some commercialized “wildflower garden” seed mixes contain a wide range of annuals and perennials to fill a garden. I tend to avoid blends because I like to be more intentional around plant placement and develop drifts of the same species.

My favorite starter seed types to spread in the garden:

  • Blue grama grass (Boudeloua gracilis)
  • California poppy (Eschscholzia californica)
  • Sunflower (Helianthus annum) — the regular wild kind. I often use plain bird seed! It’s cheap in bulk, and the plants are drought-tolerant and multi-flowered, grow quickly in any soil and attract birds.
  • Blanket flower (Gallardia) — this is a short-lived perennial but often blooms the first year
  • Penstemon species — if the garden is dry or non-mulched, they should have a good establishment rate. In thick mulch they may not.
  • Prairie coneflower (Ratibida pinnata)

Finally, when the core garden plants are in place, you can add dimension and detail to the garden by introducing a few non-spreading accent plants that hold their own against their aggressive neighbors. Some of them are tall spires that break through the surrounding plants. Some start growing early in the spring to avoid competition. The rest line the garden’s edges and paths, where bright sun reaches lower levels.

Some of the showier, non-spreading meadow garden companions include:

  • Blue oat grass (Helictotrichon sempervirens)
  • Various non-creeping Sedums, although some groundcover sedums can fill gaps as well
  • Blue fescue (Festuca glauca)
  • Daylillies (Hemerocalis)
  • Foxtail lily (Eremurus)
  • Prairie blazing star (Liatris spicata)
  • Fall-planted bulbs, particularly Alliums: Allium ‘Purple Sensation’ (Allium aflateunense), Allium ‘Purple Rain,’ ‘Drumstick’ Allium (Allium sphaerocephalon), species tulips, particularly Tulipa clusiana and Tulipa bakeri.
By late sumner of the first year, you can already see many of the new plants filling in. The Russian sage, which has grown large in this photo, was part of the previous garden in this spot so it is much larger than the new plants. Summer 2020.

Maintaining the garden


Few garden plans are so perfect from the get-go that you don’t need any tweaks. You may find a species doesn’t fill in the way you’d like, or that you’d like to expand the color palette. Plan on adding a few more plants here and there as time goes by. You might even choose to toss in a few handfulls of seed. A caution: when over-seeding a garden, I favor adding single species in a section at a time. Although this garden style allows plants to mingle, too many different species growing in the same patch can cause detract from the desirable contrasts found in larger drifts.

After about a year since it was planted, you can see that the meadow garden has already filled in well and is putting on a colorful display. June 2021.

Ultimately, meadow gardens can be very low-maintenance. Weeds have a hard time finding an opening among densely-packed, tough established perennials and grasses. Dead flowers set seed that feeds birds and adds winter interest. Insects and animals move in, enjoying the shelter and food source and keeping each other in check. Pest insects are unlikely to become a nuisance when plant varieties are very diverse and predatory insects are always present. All you have to do is sit back and watch, or do as much or as little as you’d like.

Another view of the Westminster, Colorado garden in early summer 2021.

When to trim back

One popular approach to meadow gardening is to cut dead stems down in late winter, just before green shoots emerge. I leave the downed material in place as mulch. Spring rain and snow will quickly soften and compress it as it is covered by new green growth. Earthworms tug the dead leaves into the soil so they soften and partially decay, at which point they become the worms’ food. You can choose to spot-trim things that bother you or become overgrown, and gently nudge your plants with selective thinning. When a competing plant is ready to grow into the void, the plant you are trying to reduce will stay in check long term. But like always in a meadow garden this work always optional.

Whatever you choose, the basic perspective I employ in meadow gardening is that it’s always much less work than spraying, mowing and aerating a lawn, or reseeding dead patches and managing insect pests. And the meadow garden, with vibrant colors and textures and a host of animal guests, is a lot more fun to watch and explore as time goes on.

A primer on the cactus family, and growing mountain ball cactus, Pediocactus simpsonii, from seed

Cacti make up one of the most diverse and rapidly-evolving plant families in the world, native exclusively to the Americas.

First appearing about 35 million years ago (fairly recent for such a large group of plants), the first cacti were thorny tropical shrubs with woody stems and lush leaves. They’re hardly recognizable as cacti, but you can still see these ancestral plants in the genus Pereskia.

A leafy cacti from the genus Pereskia growing in the Kona Airport gardens on the Big Island of Hawaii, hardly recognizable as a cactus except for the clustered thorns on the stem emerging from structures called areoles that are unique to cacti.

Nature’s high-tech survivors

Cacti employ an advanced type of photosynthesis, in which pores only open at night in cool temperatures to absorb carbon dioxide. They bind carbon as malic acid, a very weak acid found in many life forms, in special cell organs called vacuoles. They close their pores at dawn, before the air heats up, then draw four-carbon malic acid molecules into chloroplasts during the day to use it in photosynthesis without losing water to evaporation. Only a few plant families in the world can do this, allowing them to make glucose with minimal water loss. The same process arose independently in bromeliads, orchids and a few other groups.

Many of these carbon-storing plants are succulent, since thick fleshy tissues create more space to store carbon. That trait provided an added benefit of reducing the mass-to-surface area ratio which further limits evaporation, and storing lots of water, for a second level of drought-resilience.

With these evolutionary tools in tow, cacti quickly colonized areas other plants couldn’t. They lost their leaves, climbed into trees in the rainforest where they could grow without soil, advanced up dry rocky cliffsides and mountains, and eventually developed the familiar spherical, paddle and columnar shapes widely recognized as cacti. They then spread into extremely hot and dry areas west of the Andes and across what is now Mexico and the American Southwest.

The most famous cactus, the saguaro, grows in the Sonoran desert where the region’s average 10-15 inches of precipitation per year come in relatively short downpours followed by many dry months. Additionally, rainfall can vary widely year to year—some years receive up to 20 inches of rain and others as little as two. To grow large, plants need to be able to quickly absorb water when it is available and draw from reserves over many months, which cacti do by swelling and gradually contracting.
An epiphitic cactus clings to tree bark in a tropical rainforest. It is able to grow without soil thanks in part to its water-saving biology.

The cactus family’s evolutionary diversification has been remarkably fast, with new cacti species appearing every few thousand years to give us some 2,000 documented kinds today. But because of the tropical origin—to the chagrin of northern gardeners—most cacti are still unable to survive cold winters.

In the cactus family, the genus Opuntia has the most species that can survive sub-freezing temperatures.

The genus Opuntia, or prickly pears, are one exception, a large genus containing a lineage that rose with the Rocky Mountains and eventually spread to the plains, eastern U.S. and Canada. Another is the genus Pediocactus.

The Mountain Ball Cactus of the Mountain West

Pediocactus simpsonii, or mountain ball cactus, is one of the hardiest cacti outside Opuntia. Native to the high plains, Rocky Mountains and sagebrush steppe valleys of the western U.S. up into Idaho, Oregon and Montana, the cactus clings to shallow gritty or powdery soils among thirsty pine tree roots and nestled under tufts of bunchgrass or between rocks.

This hardy cactus can reach 11,500 feet in altitude and survive temperatures of 35 degrees below zero (-35°F). It grows to around 3 inches tall by 3 inches wide as single plants or small clusters. Unlike some other globular cacti, it is tolerant of part shade, and in hot dry weather it partially dehydrates and shrinks downward to hide from the sun or herbivores. The small globes plump up with snowmelt or rains in early spring, when they bloom and set fruit, spread by birds.

For a long time I thought these cacti were rare, though perhaps I wasn’t looking close. During the spring of 2021, when most of the Western U.S. was gripped in drought, the grass and wildflowers grew unusually thin, exposing the little cacti in their multitudes.

On a family member’s undeveloped 5-acre property in the foothills west of Berthoud, CO, I came across dozens of them around the bases of planted pinyon pines where they seemed to thrive despite the competition of thirsty tree roots. With permission from the owner (my grandma, who until then had no idea the cacti were there) I picked a few fruits, smashed and strained them and collected the seeds. There were dozens in each crambeery-sized fruit, each one a very hard black sphere about the size of a poppy seed.

Weeks later on a camping trip on BLM land near Radium Hot Springs, a dry forest of pinyon, juniper and sagebrush between higher Rocky Mountain ranges, I found literally thousands of mountain ball cacti—a cluster every few feet among the sagebrush and around the drip lines of pinyon trees. At around 8,000 feet, they were early in the growing season and just starting to bloom.

A pair of Pediocactus simpsonii cacti in a sagebrush meadow in a pinyon-juniper forest close to Radium Hot Springs near Kremling, Colorado.

Growing Pediocactus from seed

Pediocactus seeds are reputedly difficult to sprout. Like many plants that thrive in harsh climates, they have internal barriers that ensure their progeny hide away in the soil for years or decades until an opportunity arises. This is commonly referred to as seed dormancy which prevents seeds from sprouting even when they’re moist.

Triggers could include mild spring weather after freezing, a wildfire that clears the ground of competitors, a flash flood that shifts the soil, a dry spell that leaves gaps in the grassland or just the advance of time. Thar way, droughts or events that injure the established plants or leave them unable to bloom for decades won’t wipe out the population as a whole.

The best way to grow the seed, according to most sources, is to plant them in containers outside in a suitable climate and simply wait for the best conditions to occur naturally. That could take six months to a year and even then may only get you a moderate germination rate. With a few contradicting, anecdotal accounts about the best way to grow the seed, I thought I’d subject my seed collection to a science experiment to improve the odds and come to a more objective answer.

Testing various methods of germinating Pediocactus seeds

To test my seeds, I the collection into plastic bags with paper towels and introduced them to a variety of conditions. One bag was not given any treatment, two were scoured with fine sandpaper, one sanded batch and one unsanded batch was moistened and frozen and thawed several times over about two weeks, and one was subjected to the same freeze-thaw treatment dry. Another was wetted with hydrogen peroxide and left at room temperature.

After the treatment, the seeds were planted in a seed tray with mixed sand (50 percent), potting media (25 percent) and vermiculite (25 percent), packed down and covered with an additional 1/8 inch of sand and potting media. The seeds then went into a clear plastic bin and set outdoors for light and warmth to germinate.

At about three weeks in, I’ve spotted my first seedling—a tiny green sphere no bigger than a grain of sand, in the hydrogen peroxide row. That surprised me! I was expecting the sanded+frozen+thawed seeds to emerge first if any did at all.

The first seedling, in the hydrogen peroxide treated (center) row, is barely visible in the lowest cell of this image.

I’ll keep updating to follow the progress of this batch.

What is a crevice garden? An intro to a fun and attractive trend in xeriscape

A crevice garden is a style of garden arranging rocks in layers sticking vertically out of the ground. Originating in the Czech Republic, the crevice gardening style mimics natural rock features and plants growing from cliffs and crags. This charming practice is increasingly popular in the United States, particularly Colorado.

An alpine crevice garden at the Denver Botanic Gardens.

Thousands of species of plants around the world are adapted to grow in small spaces between rocks. In some cases they are so accustomed to this life that the plants—sometimes classified as lithophytes—are difficult to cultivate in typical garden soil. Crevice gardens employ plants with long, wiry, penetrating roots that find water supplies deep in the rocks, but loathe being excessively wet at the base of the stem, and don’t fare well with competition from larger plants.

Additionally, many plants that grow fine in garden soil can adapt to rock crevices—plants like huchera, penstemon, creeping phlox, candytuft, lupines, ajuga, dianthus and more. In nature, cliffside plants even include some trees, which will attain a more compact, dwarf form under the confining conditions. When native pines grow in tight confines they develop natural bonsai appearance and can live for decades or centuries without getting more than a few feet tall.

In a newly-planted crevice garden in my garden, sedums, sempervivums, Pediocactus, Ajuga reptans and Liatris punctata coexist happily despite having varying water needs in a standard garden.

Crevice gardens counterintuitively support plants that need dry conditions to thrive, as well as hosting plants that like moderate moisture, since the roots can reach deep into wetter spots within the rocks. They do this by allowing the root tips to stay wet while the crown stays dry. Plants in these spaces also benefit from not having to fight the aggressive root systems of nearby grass, shrubs and trees.

This is a great technique for growing small succulents and cacti that get lost in an expansive garden, which is helpful because many cold-hardy cacti and succulents are very small and are best viewed up close. Pediocactus, sempervivum (hens and chicks), dwarf prickly pears and small sedums thrive in the cracks. It’s also ideal for many other native Western species adapted to the dry southwest or high Rockies.

Finally, a crevice garden is a great way to garden in the city with a small space! With a few square feet you can plant dozens of small, attractive plants, each in its own spot, without any being overtaken by the others. It is remarkably weed-resistant, is virtually maintenance free, and combines the aesthetics of stone structure with the seasonal change and movement of live plants.

Collecting wild plants for gardens: how to forage responsibly

If you like gardening and native plants like I do, you know there are some mixed messages about collecting wild plants. We hear growing native plants is good, but only if they come from reputable commercial nurseries. We’ve learned the harms of picking a wildflower, but give little thought to building with wood, meaning somebody harvested an entire tree from a forest. We understand hunting and fishing is legal with a permit, but what about plants?

Of course concerns about proper use of wild spaces are well-founded, but you’ll come across a confusing mix of sentiments. Since native plant enthusiast communities are typically pretty pro-environment, sometimes it seems like those who want to make the tiniest impact bear the most scrutiny.

The truth is, all cultivated plants came from the wild at some point. And there are many benefits to getting more diverse and more local plants in our gardens than what nurseries currently offer. To do that, we need to learn the legal, respectful and ethical ways to collect wild plants.

Your resources: the Bureau of Land Management, Forest Service and U.S. Department of Agriculture.

If you live in the United States, there are several federal agencies to help manage public resources and wild plants. They provide information and guidance for free, since working with the public is part of their mandate funded by taxes. BLM land is by far the easiest to collect on, and depending on what you’re going for, hobbyists may not even need a permit (though ethical principles still apply). National forests also exist for managed harvesting and allow regulated collecting by the public. Collection permits cost as little as $20.

If you plan on traveling large distances with plants you collect, such as from Hawaii to the mainland, you can seek guidance from the USDA.

Know what kind of plants you’re looking at

In some parts of the world, poaching rare plants is driving species to the brink of extinction. Some of the most common targets are carnivorous plants, certain cacti and succulents, orchids and bulbs. Their unique shapes and features make these plants stand out, and slow growth makes them hard to propagate, so nurseries can’t keep up with demand. Unfortunately, their slow growth also prevents wild populations from recovering from constant harvesting. Before you disturb wild plants, identify them well enough to be sure you’re not threatening any vulnerable populations.

On public lands where collecting wild plants is permitted, the National Forest Service or BLM will provide vulnerable species lists. But even if you are on private land with permission from the owner, it’s better to leave vulnerable species intact.

Harvest seeds or cuttings rather than whole plants

When a plant is producing seeds, the least disruptive collection option is to harvest a few seeds and leave the plant intact. If there are no seeds, a small twig or stem cutting lets the plant recover. If that’s not an option for the species, consider taking a basal cutting—a rooted stem or shoot from the base of a clump-forming perennial—without digging up the whole plant. All these methods reduce the need to deprive the area of a whole, healthy plant.

Artemisia ludoviciana cuttings, prepared from a single stem, cut into segments and prepared to be stuck into a rooting media.

Collect only the plants you can keep alive

Another reason to ID plants you want to harvest is to be sure it’s a species you can propagate. It’s wasteful to start digging at unidentified plants only to discover they have deep taproots you’ve broken off and doomed the plant. Trying to collect wild plants you don’t know how to transport or grow can lead to waste as well. Be sure you have a field guide, access to a digital database, and a cooler or container to keep cuttings cool, protected and humid for the rest of your trip.

Keep a light footprint when collecting wild plants

Evaluating a prospective collection is about more than that individual plant. Survey the other plants of that species in the area. If you see other signs of collection, move to a new area. Make sure there are other plants of the same species around. (The rule of thumb is to not collect more than 5 percent of the plants in a small area, or 1 in 20 plants.) Don’t take the largest or healthiest individual, and don’t take the only seedling if there aren’t several other seedlings nearby.

My own advice: don’t overlook common and non-showy plants

There’s no doubt that a cluster of native wildflowers is a lovely sight. Most wild plants taken into cultivation as ornamentals are the showiest species, then bred to be even showier still. But if your gardening goal is to widen the domain of the ecosystem and to invite birds and insects to make use of your land, the keystone plants—the ones that are so abundant and dominant that they define the ecosystem’s boundaries—are valuable to incorporate.

These wild-collected whiplash daisies, cool-season bunchgrasses and artemesias are from a private property with permission. None are rare or showy, but I think they are appealing in combination—something to keep in mind collecting wild plants.

Importantly, plants that don’t bloom brightly or tower above the others are underrepresented in native gardens. Depending on your region, that could refer to prairie grasses, sagebrush and other artemisias, rabbitbrush, milkweeds, sword ferns or others. It’s a challenge, but also a great benefit, to incorporate these plants into your garden—to evoke not only the floral color but also the texture and character of the wilderness.

A garden of Colorado native artemisias and grasses, with just a few native flowers scattered in. This will form a handsome naturalistic texture when it fills in.

Bringing tropical cuttings and seeds to life

If you love plants, coming home from a trip with a bunch of seeds and plants in tow is like adding an extra day to your vacation.

All but a single one of these bags was approved at the USDA checkpoint to travel from Hawaii to the mainland, since the U.S. government is primarily concerned about the risks of transporting pests contained in commercial crops and fruit. As tropical plants washed free of soil, pulp, cotton, leaf spots and bound for a quarantined indoors setting, there’s little risk that any would become invasive threats in Colorado’s snowy climate.

Like an 8 year old back from trick-or-treating with a cache of Halloween candy, you spread your bounty out over the kitchen table and sort through what you got. After making some quick strategic plans, it’s off to the local garden store to buy some extra seed trays and plastic domes to get started.

Out of the dozens of types of plants I got though the USDA inspection in Hawaii, I feel relatively confident I can grow all but few. The philodendron vines and Monstera are notoriously easy to propagate from stem cuttings, even in plain water. I have two types of Crinum asiaticum (spider lily) seeds, which I’ve grown before and know they’re basically foolproof. Croton cuttings are also fairly easy to root in soil or water, although one of my cuttings is looking pretty wilted after shipping and I’m not sure if it will make it.

A batch Crinum asiaticum, or spider lily, seeds planted in a simple seed tray in vermiculite and potting mix. These are very easy to sprout—I figure all 6 out of 6 will survive.
An African tulip tree in Kona covered with flowers and big pods full of seeds.

One species I’m less sure about are the Spathodea campanulata seeds, known commonly as the African tulip tree, which reportedly have low germination rates. The pod I found on a tree growing next to a parking lot in Kona contained what looked like thousands of seeds—a dense, loose mass of flat, lightweight seeds, each imbedded in a thin cellophane-like sheet of tissue. Even the slightest breeze scatters the ultra-lightweight seeds into the air, where they flutter around like mosquitos. (This was an annoyance to the group I traveled with, when a swarm sparkly seeds blasted out of the pod on the dash and into the cab when the air conditioner came on.)

The seeds are plentiful and extremely gregarious travelers, but this plant’s reproduction strategy to is to produce its seeds en masse and allow them to spread far, with lower emphasis on each one’s viability. I’m worried there’s a chance the entire batch dried out too much while it was still on the tree and none will sprout.

The seeds of the African tulip tree are extremely lightweight and plentiful. This bag of seeds came from a single, banana-shaped pod. Although the seeds have a relatively low germination rate, it’s easy to see how Spathodea campanulata has become such an aggressive invader in tropical forests where it has been introduced outside its native range. These are headed to a seed tray to see if any will sprout, and will remain indoors as houseplants if they do.

I’m also less sure about the single, grape-sized seed pod I found in a refuse pile in the Maka’eo walking path garden at the old Kona airport (an amazing garden to visit if you are ever in the vicinity, by the way). I thought I knew what it was—I initially thought it was a Euphorbia neohumbertii—but now I’m looking that species up and having some doubts my ID was correct. In any case, the three seeds, which fit snugly in the three-chambered pod and have hard casings that resemble pine nuts, seem like they might be temperamental when it comes to watering the right amount. (An aside: these gardens are amazing place to visit if you are interested in looking at a wide range of tropical plants and succulents. But, though the gardens are unguarded, please don’t pluck any attached plant parts or take out any fallen fruit or other useful material. The gardens are maintained by local people, and theft of valuable plants and food crops has been a problem there).

Finally, I have some seeds from an Aloe of some sort that was absolutely covered in open pods, and a sandwich bag of seeds rom a large planting of Stapelia (also known as “carrion flower”) in Kona that was spewing its cottony fluff all over the sidewalk and beyond. The Stapelia pods look remarkably similar to those of milkweeds, as do the seeds themselves, so I looked the genus up and found Stapelia comes from the same subfamily as milkweed, Asclepiadoideae.

A mound of Stapelia, or carrion flower, growing at the community garden in the old airport in Kona. It turns out, Stapelia is in the same family as milkweed.

(It’s fascinating, the connections you can make when you know a bit about taxonomy. You can walk into a new environment, knowing hardly anything about the plant species there, and quickly identify a bunch of plants with Google by searching your location + the plant family or genus a specimen seems to belong to).

In any case, I have never grown Aloe nor Stapelia from seed, and sometimes these drought-loving plants can be temperamental to water properly in shallow trays. So we’ll see what happens.

I’ve been fascinated by the seeds from a Delonix regia tree, also known as royal ponciana or flame tree. Coming from an enormous dangling pod, which I left in Hawaii to reduce the risk of carrying pathogens, the seeds look like elongated beans. But unlike beans they come in a waterproof, waxy casing that prevents them from swelling even when soaked in pure water. It’s a strategy many plants and trees employ to encourage their seeds to last longer before they sprout, which gives them more of a chance to spread far and wide or emerge at the right times.

Many varieties of Lupine have a similar seed coating, which makes sense because they are also members of the Fabaceae or pea family, and this is something that can make their propagation more complicated. In the case of Lupine, the translucent seed coating is degraded by winter freeze-thaw cycles, fire, or long periods of time in general, helping the plant to get at least some of its seedlings to lie dormant in the seed bank and spring up in optimum conditions in early spring or after a wildfire clears competitors away. But Delonix regia, a tropical species, doesn’t live with cold winters or with recurrent fire (as far as I know). Instead, I wonder if the casing naturally dissolves in the stomach of an animal or bird, and sprouts great distances away in piles of poop.

In any case, I set seven seeds to soak in a tray of water and none of them looked any different after 24 hours. As a test I scoured the corners of two seeds with a piece of sandpaper, and sure enough, they began swelling from the scoured end, stretching and ripping the waxy coat apart until the entire seed had swelled.

Delonix regia (flame tree) seeds soaking in water. The two larger seeds were scoured at one end with sandpaper, allowing the seed to swell with water and break out of the waxy waterproof coating. The rest look exactly like they did before they went into the tray.

I’m also unsure about the viability of the Terminalia catappa, or sea almond seeds, which were easy to find all over the beaches in Hawaii. Supposedly these too are fickle to grow from seed—many of the seeds cores rot out during the long time that passes between the moment they fall and when the right conditions come along to germinate. The interestingly almond-shaped, lightweight, corky seeds evolved to float in sea water and colonize distant beaches, but are hard to pry open and I was unable to cut any open with the tools I had on hand during my trip. I’m excited about the seeds because the attractive, large-leafed trees seem to be a potential substitution for fiddle leaf figs, which are extremely trendy houseplants, but, in my opinion, are not well suited to life indoors. Fiddle leaf figs are just too finnicky, languishing in the low-light conditions in most homes and developing unsightly spots or dropping leaves at the slightest provocation.

Clusia rosea is another candidate I hope to use to fill the role of the fiddle leaf fig, and I got a few tiny seeds along with some cuttings. The seeds are small and come imbedded in a sticky orange goo that helps them attach to mature trees in a wet forest, germinate on a branch, send aerial roots down to the ground and ultimately overwhelm or strangle the unfortunate host tree. The seeds dry out and die easily (I planted six and the rest were dry and dead within a day), but the cuttings seem resilient, staying very plump and green in transport.

Additionally, there are some dry Pandanus tectorius (screwpine) seeds in my cache, a rare Hawaiian native plant that happens to be extensively cultivated, and I was able to collect the dry seeds from the lawn at a resort.

I’m fortunate to be somewhere with a lot of light, and the plants are getting started in a humidity dome to help them root and also give me a chance to discard any that show signs of flies or disease. However, they’ve all been rinsed and soaked, plucked and preened, and have had any spotted or damaged leaves removed. I’m not expecting any problems, and can’t wait to see what some of them turn out like.

A cutting of Clusia rosea, or autograph tree. I have no experience with them but I think they will be very easy to root because the cuttings are still plump and green with no wilting even after days in transport.

Botanical tourism: bringing plants from Hawaii to the mainland

When I was a kid, my dad sometimes brought me bits of plant life from his work trips around the country. I was more interested in those kinds of souvenirs than anything from an airport gift shop.

They were nothing ecologically-sensitive or fancy. Just nuts or seed pods from trees in a public park, or sprigs of foliage from a buffer strip along a parking lot. I remember a husk of horse chestnuts from Washington DC, a handful of Agave bulbils from San Diego, and lots of pine cones.

It turns out I now travel the same way. But unlike my childhood gifts, which I usually dried and arranged on what I dubbed the “science shelf” in my bedroom, I’m more interested in things I can propagate. I find that having a story behind my houseplants gives me a deeper interest than just buying them at a garden store.

So, on a recent trip to the Big Island of Hawaii, I took the opportunity to collect some really interesting and beautiful plants, with the added challenge of following the stricter regulations of traveling over an ocean with cuttings and seeds.

Me and Jeff on the Big Island
Jeff (holding the camera) and me on a trail on the Big Island

Traveling eco-safe with plants

Over the years we’ve learned more about the risks of moving living things around the world. Every day, millions of tons of timber, grains, livestock, plants, flowers and produce are shipped across the oceans. Many have escaped into the wild, becoming invasive species that overrun native ecosystems. Others harbor hidden pests that could wipe out species or destroy agricultural industries. Consider the American Chestnut, a once-dominant North American tree that was wiped out a century ago by an exotic fungal disease, or the emerald ash borer, a bug from Asia that is steadily eradicating North American ash trees.

As much as I love collecting plants, it’s important to me to do it safely and legally. I would hate for my legacy of life on Earth to have been personally responsible for destroying a species. So I follow the regulations and take some additional precautions. That also means being above-board with the USDA and any other relevant agencies.

Safe vs unsafe plants

Living in Colorado, it’s unlikely a tropical plant brought from Hawaii would survive outdoors and become invasive. These are strictly to become houseplants, isolated from the local flora. But that’s not the case if you’re in a balmier state, like Florida, Texas, California, or even marginally similar places like Arizona or Oregon, so there will be stricter considerations than what I describe here.

A few categories of plants contain species that are remarkably adaptable and widespread, and the U.S. Department of Agriculture prohibits their transport entirely. They can also harbor viruses, fungi or insect pests that can more easily jump from one climate to another. That list includes grasses, sedges and cacti, as well as most commercially-important vegetables and fruit. In the case of cacti, an extremely destructive cactus moth was brought to Hawaii to eradicate an invasive Opuntia species, burrowing deep into the flesh and eating it from the inside. The moth could put several North American prickly pear species at risk.

Plants must be soil-free

Moving soil is a concern unto itself. A handful of wild soil can contain hundreds or thousands of species bacteria, fungi, viruses, insects, worms, nematodes, slugs and snails or various pest eggs. Some of these species may not even be documented by science yet, and it’s likely there are organisms there that can live in both tropical and cold climates. Due to the incalculable risks, moving soil into the U.S. mainland from overseas is banned entirely. Plants need to be bare-rooted and washed, or better yet, restricted to dry seeds and soil-free cuttings. Potting media, which is an artificial product made of pasteurized dead plant material and fillers, is not soil, and that’s what nurseries cleared for shipping to the U.S. will use.

My experience collecting plants in Hawaii

Hawaii has an impressive variety of landscapes and microclimates. In the rainforest biomes, you can really get a sense of the risks posed by invasive species when you realize that almost all the trees and vines growing there came from someplace else. From the dominant eucalyptus trees to the ubiquitous pothos vines, the wettest zones are basically a hodgepodge of aggressive plants from jungles around the world. The ecosystem there is basically a brand new assortment of organisms, and we’re yet to see how it develops over coming generations.

This jungle on the Big Island’s northwestern coast is captivating, but most of its plants come from elsewhere and have overwhelmed the native species.


The resorts and villages, meanwhile, are manicured collections of what I basically think of as houseplants. The giant banyan trees, with curtains of aerial roots dangling from the branches, come from a group of Ficus tree species that grow in the wild by sprouting from seed on branches of mature trees and eventually smothering them with their roots (strangler figs). They include the familiar “weeping fig” and “rubber tree” which we know of as houseplants. There are hedges of hibiscus, beds of crotons and bromeliads, Monstera vines climbing the trees. There are Sansevierias and Heliconias. Aloes and Agaves. Everything you’ve seen in your local nursery’s tropical section is now here, giant-sized.

And that’s where I got almost all of my cache. The gardeners coming through to trim the plants on practically a daily basis provided lots of cuttings, and the seeds scattered around the ground made good finds. Tropical trees tend to be heavy seed producers and nearby sidewalks and streets are littered with them.

Whenever I found a cache of seeds or downed branches that looked appealing, I looked the species up to make sure I thought I could grow it at home. Before the week was up I compiled a cooler’s worth of seeds and cuttings, bagged, labeled and ready to go.

Going through the USDA checkpoint

Getting live plants to the mainland is an intimidating thought, given that you can’t even bring an orange for lunch onto an airplane headed to North America. But the regulations are there to prevent specific pests from getting across, and due to the millions of pounds of commercial food crops shipped around the world each year, some of them have unfortunately already gotten to Hawaii—but some have not yet reached the continental U.S. Others have reached the continental U.S. but aren’t yet in Hawaii, so restrictions go both ways. Additionally, there are a lot of pests that hide in fruit in particular. If you want seeds, which are less hospitable to stowaways, just make sure to scrub the flesh off and put clean, dry seeds in a package for inspection.

Cuttings and seeds are cleaned, dried, bagged, labeled and ready to go through USDA inspection to bring to the mainland.

Cuttings are, similarly, surprisingly easy to bring. As long as they don’t come from a list of prohibited plants (which includes plants in the citrus family, cacti and grass), and they’re not endangered (which they wouldn’t be because I only collected cultivated plants), they’re likely permitted.

In this case, you want to remove any leaves with bruises or spots that could potentially harbor disease. Luckily, many tropical plants are vigorous enough that they can grow from a segment of stem without any leaves at all.

It’s probably important that you are able to identify the species you are working with, in case the USDA agent doesn’t recognize it and wants to exclude it. Or, worse, the USDA agent could accidentally miss a prohibited species and allow it through. Make sure you read and can understand the guidelines. If you have any doubt, you can call the Hawaiian USDA office, which I did, and get connected to someone who can offer guidance.

I went through the checkpoint at the Kona airport on the Big Island with 27 types of plants and cuttings. The agent only blocked one item from getting through—a bag of Crinum asiatica seeds that were still very green and fleshy. She picked out a couple other seeds here and there that looked damaged, letting me keep the rest. She took a close look at some agave bubils to make sure they weren’t some type of cactus, and that was that. After inspection, the plants went into a cooler that was tagged with a USDA sticker, and arrived in Denver for me to process and propagate.

Additional safeguards

After getting my cuttings home, I’m still not going to take any chances that some unusual organism slips through. They are being nursed and propagated indoors, in most cases under a plastic humidity dome. That way I’ll be able to observe them for some time as they get growing. You can read a bit about general plant propagation techniques here. But in my next post, I’ll write more about bringing these particular little stems and seeds to life.