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Onions are not just for the vegetable garden!
Most of us are familiar with the edible varieties belonging to the onion or allium family, which include garlic, chives, leeks, onions and shallots. There are, however, many unique and eye-catching species of ornamental onions in the allium family that are fast becoming popular additions to the flower garden.
These bulbs are some of the easiest to grow and love our sunny, dry climate. Seldom bothered by insect pests or diseases, most allium bulbs are moderately drought resistant, a big plus considering our year of drought conditions and water restrictions. Their strong, sturdy stems rarely need additional support and some will attract butterflies and bees. Once established, alliums require minimal care and will grace your garden year after year with their sensational, richly colored blooms.
The best months for planting these fall-planted bulbs along the Front Range are September and October because this allows enough time for a good root system to form before the ground freezes. If planted later than October, they may not have time to develop properly, which could cause erratic flowering in the spring.
Planting depth is usually about four times the height of the bulb, figuring from the soil surface to the tip of the bulb. Since allium thrive in well-drained soil; amend the planting area by adding organic matter such as compost or well-rotted manure to a depth at least a couple inches deeper than you'll be planting the bulb. Some phosphorus fertilizer can be applied at planting time and should be placed in the root zone as well. Water generously after planting. After the ground freezes, apply mulch three inches deep to help prevent damage to bulbs caused by the freezing and thawing cycles that occur during the winter months.
Water regularly during the growing season, especially when the leaves and flowers are present. Many allium varieties seed out readily and if new plants are not desired, simply remove the seed heads before they have a chance to scatter their seeds. Planting alliums among other plants may help hide those sturdy stems and leaves that start looking beyond their prime after flowering.
Ornamental onions vary considerably in size, shape and color, from petite gems, perfect in rock gardens to towering giants, adding interesting dimension to back borders.
Allium giganteum (Giant Onion) is the mammoth of the group, standing 4 to 5 feet tall and producing a colossal, purple colored sphere with hundreds of tiny florets. This unique specimen prefers a very sunny exposure, blooms in early summer and can be electrifying in the back border of the flower garden.
A smaller but no less magnificent species is the A. aflatunense. This beauty tops out at 2-3 feet and features a dense 3-4 inch, perfectly round head of lilac-purple starry flowers. Blooming in late May and early June, this variety can create drifts of stunning flower balls if planted in groups throughout the garden. If you prefer deep purple flowers, select A. afatunense, 'Purple Sensation.'
Hailed as one of the larger and most dramatic allium is A. christophii (Star of Persia). In June, violet-lilac flower heads up to 10 inches across spring from a 1-2 foot stem. Iridescent, star-shaped flowers cover the heads, resembling a Fourth of July sparkler. This allium is an amazing addition to any perennial bed especially when planted in a large group. They are exceptional for fresh or dried flower arrangements and perform well in drier conditions.
A. sphaerocephalum (Drumstick Allium) produces burgundy-red flowers in tight golf ball size ovals supported by sturdy three-foot stems. This allium is adored by bees and blooms in July.
A.karataviense produces intriguing broad, long leaves with an exceptional bluish green color. Ten to twelve inch stems support 3-5 inch round flower clusters. Blooms begin in late spring to early summer and come in a medley of colors, ranging from beige-pink to reddish-lilac. Consider this one for rockeries and similar dry places.
Moly, or A. luteum, also known as lily leek or golden garlic, is the darling for naturalizing and does well in partial shade. The striking clusters of citrus yellow flowers are produced on 12-inch stems, blooming in late May to early June. Moly can create little rays of brilliant sunshine in your garden when densely planted.
Ostrowsky, or A. ostrowskianum, is a pretty 7-10 inch dwarf species with fairly large heads of reddish-pink flowers. Each bulb produces a mass of bloom in June and the plants spread rapidly.
There's even an allium for Colorado mountain gardeners! For those of you living in hardiness zone two or three, try A. caeruleum (azureum), also known as the blue globe onion or blue garlic. It produces sky blue blooms on two inch round clusters in late spring and grows about 12 inches high. This one is especially good for drier areas and loves full sun.
These ornamental onions can add incredible dimension and dazzling beauty to any flower garden and now is the time to plan. Local nurseries will probably begin stocking allium bulbs as fall approaches and many garden catalogues feature the fall bulbs.
Create a new look in your garden by planting some of these exotic eye-catchers and watch the fireworks explode into spheres of colors next year.
For more information, see Colorado State Extension fact sheet 7.410, Flowers-Fall-Planted Bulbs and Corms, at www.ext.colostate.edu.
For more information on Gardening, contact your
local Colorado State University Extension office.
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