Regional Gardening Reports :: National Gardening Association

In the Garden:
Upper South
September, 2011
Regional Report

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Ornamental onion Globemaster is among the most spectacular. Photo courtesy of John Scheepers Flower Bulbs (

Big, Bold Flowering Onions

No winter would be survivable without the January flowers of snowdrops, nor can I imagine not breathing in the luscious scent of hyacinths or reveling in the glorious colors of daffodils and tulips. Yet each fall, as I add bulbs to the garden in anticipation of month after month of flowers next spring, I never want to be without that grand exclamation point to the season, the spectacular, large-flowering onions, or alliums.

Usually blooming as the last of the tulips finish, the large ornamental onions ably assist filling in the flowering gap for three to four weeks between late spring and early summer. They make admirable companions to other flowers at this time, such as peonies, catmints, or baptisias. As to colors, shades of lavender, purple, and mauve predominate, but there are also ones with white flowers. The globe-like clusters (called umbels) of small flowers (called florets) vary in diameter from a modest 4 inches to a show-stopping 12 inches atop naked stems ranging from less than 12 inches tall to 3 or 4 feet. An added incentive to growing ornamental alliums is that they are generally deer- and rodent-resistant, plus the flowers are beloved by bees and butterflies.

How to Grow Ornamental Onions
Like their edible cousins, ornamental onions grow best in well-drained soil in an open, sunny location. The soil does not have to be rich, and, once established, the clumps are best left undisturbed. As to depth of planting, set the bulbs so that the distance from the top of the bulb to the soil surface is about twice the height of the bulb. Usually, this is about 6 to 8 inches. Among the most expensive of the spring-flowering bulbs, start with at least three of any one variety, then add more each year, if possible, up to about twelve in an irregular grouping, spacing the bulbs 10 to 12 inches apart.

With some varieties, the long, strap-shaped leaves can look raggedy just as they are coming into bloom. One gardener I know plants his alliums behind a low boxwood hedge, thus hiding the foliage while still making a dramatic statement in the garden. Be creative in thinking of other ways to camouflage the leaves. One popular way is to plant them among daylilies.

Large Ornamental Onions to Try
Ornamental onions have had a tough life with regard to proper scientific naming, with a number of changes back and forth over the years. No doubt, as you shop for the bulbs, there will be some variation in the names, especially with the species, but the named cultivars are fairly consistent.

Of the taller alliums with the largest globes of flowers, 'Globemaster' is the most widely available and popular. A hybrid cross from 1971, it has incredibly long-lasting 10-inch globes of aster-violet florets on strong, 36-inch stems. 'Ambassador' has 7-inch globes with intense purple florets, while 'Gladiator' has 6-inch globes of rose-purple florets, both with stems to 4 feet. Allium rosenbachianum has 5-inch umbels of dark violet florets with dark mid-veins on stems to 36 inches; a sport of this, Early Emperor, blooms about two weeks earlier on slightly shorter stems.

Other large-globed alliums usually have flower stems about 24 inches tall. Among these are 'Firmament', with long-lasting, 8-inch globes of purple florets and silver anthers and 'Purple Sensation', with 4-inch globes of reddish-purple florets. 'Pinball Wizard' has 6- to 8-inch globes of silvery lilac-purple. Star-of-Persia (Allium albopilosum) has 10-inch globes of violet-colored florets with silver highlights and deep green eyes.

If white flowers are more to your liking, try 'Mount Everest' or 'White Giant', both with 6-inch globes of white florets on 3-foot stems. Another option is 'White Empress', which blooms slightly earlier with starry white florets with deep lime-green centers.

Other Ornamental Onions
With some seven hundred species of allium, there are plenty of other choices of ornamental onions for the garden. Allium karataviense has 5-inch spheres of white flowers, but the stems are only 8 inches tall. Try planting these among other low-growing flowers. Allium bulgaricum has 36-inch stems, but the white-and-purple florets are loose and dangling. The variety 'Hair' has green florets that resemble tentacles. Allium schubertii is sometimes called the fireworks allium because the 12-inch clusters of rose-purple florets on 16-inch stems resemble exploding fireworks. In addition, there are a number of ornamental alliums that are a foot or so tall with umbels of florets just an inch or two across. These usually bloom earlier in the spring.

An Extra Bonus with Ornamental Onions
Because allium blooms last a long time and have such an architectural quality, they are popular with anyone who enjoys arranging flowers. But, if you can't bear to cut the alliums when they're in bloom, don't despair. With many of the varieties, the umbels also can be dried successfully and used in dried bouquets and crafts.

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