Ornamental alliums are by no means rare or exotic garden plants. Even big box stores and grocery stores often sell the bulbs in their garden sections in fall, and the most common cultivar is Allium aflatunense, ‘Purple Sensation.’
But its ease of cultivation and showstopping quality warrants some special attention here. When I’m out tending the garden in spring and people pass by on a morning stroll, many will ask, “What are those big purple things?”
So let it be known: they are alliums. Allium is the genus that contains onions, garlic, leeks, chives and similar food plants, and the entire genus of some 500-plus species spanning the Northern Hemisphere and tropics is technically edible to humans, although not all of the species are palatable or have the spicy, pungent taste and aroma we associate with onions and garlic. Most ornamental alliums aren’t useful as food crops and ‘Purple Sensation’ certainly isn’t, but it is very showy and easy to grow.
‘Purple Sensation’ foliage emerges in early spring with the daffodils, but won’t bloom right away. In the Denver area the flowers bloom in at the beginning of May during the waning days of Darwin tulips. The tennis-ball-to-baseball-sized spherical globes containing hundreds of small violet-purple flowers stand around 2 feet tall and each one lasts about 3 weeks. Since a cluster of bulbs will produce plants that bloom at slightly different times, the display will last a month; they make a good bridge to tie in the end of the spring bulbs and the beginning of the season for bearded iris, oriental poppy and early summer plants.
When the flowers fade, the seed pods of Allum ‘Purple Sensation’ are ornamental. Foliage dies back while the flower is blooming so there is no lingering eyesore to worry about; foliage could be clipped off at the base with no detriment to the plant. However, I like to leave some of the stems and seed pods around for structural interest. As they dry, they continue to resemble fireworks, which is a festive addition to the garden or a dried flower arrangement on the Fourth of July.
Allium aflateunense is native to central Asia, the same region that hosts many species of wild tulips, and they have similar growth habits. ‘Purple sensation,’ however, is more likely than most tulips to multiply and spread. Bulbs grown in optimum conditions the bulbs can roughly double in quantity every year by division and seeds can become plants large enough to bloom on the third year after they fall. If you cut off the ripe seed pods and toss them into various gardens, it’s likely that you’ll see blooming alliums there eventually. Small bulbs produce smaller flower stalks, while large bulbs produce large flower stalks or possibly 2-3 medium-sized stalks emerging from a single rosette of leaves. After plants go to seed, they tend to gain some genetic variation and produce plants of slightly different heights and sizes.
Allium aflateunense thrives in Colorado and the Mountain West, and is slightly more forgiving than tulips when it comes to the winter cold period needed to provoke spring blooms. I’ve heard anecdotal reports that it blooms sometimes (but skips years) Northern California, but in the southern part of the state it doesn’t get cold enough and skips blooming more often than not. Where they do grow, they are drought-tolerant, hardy and forgiving plants, that provide a large colorful flower on a very small footprint that makes them a worthwhile addition to many different kinds of garden plots.