Alliums burst into glorious spheres of bloom in late spring, as jaunty and debonair as the season. Fall is the time to plant them by the dozens.
Alliums are flashy blooms by any measure. Their globe-shaped flower heads, covered with an uncountable number of tiny star-shaped blossoms, have tremendous impact in a garden.
"They really add an exclamation point," says Christian Harper, a horticulturist at Olbrich Botanical Gardens in Madison, Wis., who has been planting alliums in Olbrich's flowerbeds for more than 20 years. "There is just something about those globes from a distance," he says, "they appear to be floating, and they really pop."
The allium family of ornamental onions is dominated by great big blooms. Mail-order specialists offer the widest variety, with a dozen or more different types in some catalogs. Garden shops often have a good selection of several different alliums, usually including Globemaster, the biggest of them all, which has 10-inch purple globes of sparkling flowers on stems up to three feet tall. Globemaster's flowers last for a couple of glorious weeks in the garden. After they bloom, the sturdy flower heads remain decorative for months - at this point, they're tawny, not purple, but there's simply nothing else in the garden world quite like these big round balls, and they hold their own while the roses and daylilies come along.
Besides Globemaster, there are purple alliums with somewhat smaller orbs of blooms, white-flowering alliums, alliums with looser heads of pink flowers, and sunny yellow alliums only about 10 inches tall. Garden designers prize them all for their great beauty and for their ability to bridge the season. Like a burst of fireworks at the end of spring, alliums lead the parade of summer flowers like a tall drum major at the head of a marching band. The earliest-blooming types loom above spring's last tulips, and the latest to bloom open with the roses.
Have fun with them. "I have a favorite, and it is Allium schubertii," says Barbara Katz, a garden designer in Washington, D.C. "It's like a constellation." Allium schubertii is an atypical allium, growing on stems only about 18 inches tall. The globe of blooms, on the other hand, is about 12 inches in diameter. Individual flower stems are of several different lengths: The effect is distinctly starlike, twinkling madly.
Katz also plants "a ton of Purple Sensation" alliums in her own and clients' gardens. The dark purple blooms stand about 30 inches tall. "I mix it with hostas, and it looks like the hostas are flowering," Katz says. "I plant it around hydrangeas. It's fun."
Katz and other designers purposely plant alliums among perennial flowers and shrubs because the strappy allium foliage is usually fading when its flowers come into bloom. A lively garden covers up the tired leaves, so you can admire the spectacular flowers all the better.
Purple Sensation allium is well-known for more than its great flowers: Among tall purple alliums, it is the greatest bargain. You can buy 25 bulbs for less than $20. Globemaster bulbs often cost $5 or more apiece. Ambassador, a tall purple allium with flower heads about six inches in diameter, is another expensive one, with bulbs at about $6 apiece.
They're all worth the investment. Alliums are known for their ability to persist in a garden for years. "They're easy and long-living, almost like perennial plants," says Jacqueline van der Kloet, a Dutch garden designer whose deft hand with flower bulbs and perennials has led to international garden projects, including some at Battery Park in New York City and Millennium Park in Chicago. (Both are collaborations with the naturalistic Dutch garden designer Piet Oudolf.)
Van der Kloet included Purple Sensation and the drumstick allium, A. sphaerocephalon in her bulb plantings at the Lurie garden in Chicago. She especially loves the smaller alliums, including the white-blooming bride's onion (A. neapolitanum), which is sometimes used in bridal bouquets. Good plants to include with all alliums are "plants that are rather modest," she says, "so the alliums will add just that touch of extra that makes the combination perfect." She suggests planting them with ornamental grasses, gaura, lavenders, catmint and cranesbill geraniums.
To take full advantage of the whole allium season, plant species and varieties that will bloom over a long time. Plant them in clusters of three or five bulbs, scattered here and there in flower beds. Planted this way, "it really looks like quite a lot is going on," says Christian Curless of Colorblends, a mail-order bulb specialty company that offers 11 different alliums in its catalog. Curless says that he, like many garden designers, "think of alliums as a little bit 'in-between season' plants," but it's time to change that. They create a season all their own, and share it graciously.
Ross is a free-lance garden writer who lives in Kansas City, Mo. She writes a monthly gardening column for Universal Press Syndicate, and is a regional editor and garden scout for Better Homes and Gardens, Country Gardens, and Nature's Garden magazines.