Ornamental Onions

A pot of Turkish onions (Allium karataviense) seems the perfect ­accent in this contemplative setting.

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Nearly all of the estimated 500 to 600 species in the genus Allium are native to the Northern Hemisphere, yet only a dozen or so of the ornamental spe­cies are widely available. Many are characterized by round, puff-ball heads of flowers, and they range in size from tiny plants suitable for the rock garden to strapping giants.

One onion rises above them all—A. giganteum. It’s a mainstay of Dutch bulb catalogs, which routinely display the obligatory photo of a child holding onto the stem of this 4- to 6-foot purple lollipop of a flower. (This picture is so common that I sometimes wonder if they actually ship a blond child with large orders.)

I’ve been immune to the dubious charms of A. giganteum. Its image almost put me off ornamental onions altogether. “I only like the ones I can eat, and they belong in the vegetable garden,” I used to tell myself. I’ve learned, little by little, to eat my words. Ornamental onions vary considerably in color, size, and form. Undemanding in their cultural requirements, they make rewarding additions to beds and bord­ers. I begrudgingly admitted a few to my perennial plantings, and they gradually won me over with their good looks and usually gracious manners.

As my interest in ornamental onions grew, I discovered how easy they are to grow. No back-breaking labor is required to get them into the ground, as most are planted just a few inches deep. They can take clay or sandy soil, although most thrive best in well-drained sandy loam. All demonstrate at least moderate drought resistance, and most will rot if overwatered. Alliums are quite hardy throughout the country and are best planted in autumn. Most grow well in pots if suitable quarters such as a cold frame can be provided in the winter in the northern states. They are rarely bothered by diseases or pests. I’m hard pressed to remember so much as an aphid on any allium in my garden. Some, however, attract butterflies and bees. Most alliums are long-lived and rarely if ever need dividing. Most will self-sow in moderation; only a few are intent on world domination.

The foliage is insignificant or even negligible on most ornamental alliums; there’s no giant death scene such as that put on by prima donna bulbs such as tulips and daffodils. The leaves of many species have all but disappeared by the time the flowers bloom, so a companion plant is an aesthetic necessity to cloak the bases of the naked stems. It’s possible to exploit this trait to advantage. An ideal way to showcase smaller alliums is to plant them beneath front-of-the-border, shallow-rooted pe­ren­nials such as creeping veronicas or phlox or in the spaces between larger clump-forming perennials such as cranesbill, catmint, or lavender. The tall, thin-stemmed species can be given a spot among lower-growing companions for an airy and often whimsical ­effect.

Small wonders

Several low-growing alliums perform admirably throughout most of the country under a wide range of conditions. The lily leek (A. moly) is perhaps the best known. Native to eastern Spain and southwest France, its canary yellow umbels appear on stems 7 to 9 inches tall in late spring or early summer. It can be a lovely asset in loosely structured, partially shaded gardens. Lily leek will tolerate more shade (in some areas, the leaves tend to burn in full sun) and moisture than most other ­alliums. Contrary to oft-repeated warnings, it is not usually inclined to rampant self-seeding.

A. oreophilum (formerly A. ostrowski­anum) grows wild in eastern Turkey, the Caucasus, and central Asia. Its rose-pink flowers on 7- to 10-inch stems are a late spring delight. It reseeds, but not—at least in my experience—to a fault. Its pretty color goes with almost everything, so I’d never quarrel if it appeared somewhere I hadn’t intended. One bulb company has promoted this plant as “alpine rosy bells”. I admit it could use a common name, having been tagged with two horrid scientific names in a row, but this moniker makes me cringe.

While most onions are not noted for their foliage, one species bears striking leaves. Turkish onion (A. karataviense, named for its discovery at the Kara Tau, Kazakhstan, but widely distributed in central Asia), displays thick, broad leaves up to 8 inches long, purplish green and edged in deep red. Round flower heads the size of tennis balls with buff-pink flowers appear on 4- to 8-inch stems. The midspring bloomers thrive on drought and go dormant in summer. Turkish onion can be a dramatic accent planted in groups amid ground covers such as thyme. I pair it with Mt. Atlas daisy (Anacyclus depressus). The little daisies with red-backed petals (rays) and ferny gray leaves echo the colors of Turkish onion and share the same cultural requirements.

Small yellow onion (A. flavum) looks like a golden sparkler in midsummer. This is a variable species, perhaps due to its wide geographic distribution in southern and central Europe. Flowers vary from straw to bright yellow on stems from 4 to 30 inches tall, but cultivated forms average 10 to 14 inches. A. flavum forms clumps, much like chives, with many flower heads. It also takes partial shade.

Mountain garlic (A. senescens) comes into bloom in late summer. It’s worth the wait. Small umbels of pale pink flowers are produced in profusion on stems 4 to 12 inches tall above attractive clumps of foliage. A cultivar called Glaucum or Spirale features spirally twisted blue-green leaves; another form with straight glaucous leaves is also sold as Glaucum. Low-growing silver-leaved plants such as artemisias make excellent companions. A. senescens also makes a good edging plant. I saw long sweeps of it along a walk in Minnesota, where it was blooming its head off in early ­September. Needless to say, hardiness is not a problem for this European and central Asian native.

Medium height

As late as the beginning of the ­century, the prairies around Chicago were said to be carpets of pink nodding onions in early summer. The name of the city is reputedly taken from the Ojibwa she-kag-ong, or “wild onion place”. Gardeners might prefer this nickname to “the windy city” because the nodding onion is arguably the most beautiful of American onions. A. cernuum is widely distributed throughout North America from Canada to Mexico. The flowers vary from deep to pale pink. The 12- to 24-inch stalks bend near the top so that the flowers dangle in a charming manner. A drift of them among pinks and columbines is a gorgeous sight.

The thin leaves of blue garlic (A. caeruleum) have all but disappeared by the time it comes into bloom in early summer. The pretty, true blue spheres, slightly smaller than a Ping-Pong ball, are perched atop thin, wiry stems 12 to 24 inches tall. They can be paired with golden Coreopsis verticillata ‘Zagreb’ or ‘Golden Showers’ or planted behind a low-growing artemisia such as Silver Mound. Native to the Russian steppes, blue garlic tolerates drought.

Many gardeners—myself among them—consider Star of Persia (A. christophii) the best of the ornamental onions. I would ordinarily never even consider a flower head the size of a ­cantaloupe as anything I’d plant, but seeing is believing. Extraordinarily beautiful, each round head is composed of hundreds of loosely spaced lavender stars. The petals have a metallic sheen.

Stars of Persia, native to northern Iran and central Asia, look magical coming up and blooming through other perennials. Stems are relatively short, just a foot or so, and the narrow leaves are hardly noticeable. The flower heads are highly prized for dried arrangements. They dry to an amber color in my garden, and they look lovely even in their skeletal form. When the border looks like a candidate for a brush fire in midsummer, I reluctantly pick them. The bulbs are adaptable and drought tolerant.

A. tuberosum, Chinese chives, makes a big splash in late summer and autumn. Originating in China and the Himalayas, it has long been cultivated in the Orient for food. Its small, fragrant, chalk white flowers are held in tight umbels. Many stems 14 to 18 inches high rise above clumps of thin green leaves. The flowers of Chinese chives last for many weeks and are especially attractive with gray-leaved companion plants.

High hopes

A. aflatunense (so named for its origin in Aflatun in central Asia) grows in many gardens—or does it? As many as six look-alike species are sold as A. aflatunense. With stems about 2 feet tall, the baseball-size flower heads bloom in pleasing shades of lavender—the hue depending on which impostor inhabits your garden—in late spring. It takes an expert to identify the true species, and most of us couldn’t care less. Expect variation when ordering this bulb. Several selections have been introduced, including darker Purple Sensation, pale Mother of Pearl, and one in white.

Lucy Ball, a hybrid between A. aflatu­nense and A. macleanii, flowers in dark lilac-purple, although I half expected a flower named for the comedian to be a fiery orange the shade of her famous hair. Gladiator is a product of the same breeding with a rose-purple flower head on 2- to 3-foot stems. A. macleanii (a close relative and look-alike of A. ­giganteum) also figures, along with A. karataviense, in the parentage of the much-heralded new hybrid called Globemaster.

Globemaster is unique in several ways. It is expensive because it takes years to build up stocks of the bulb to sell at a reasonable price. (I spent a small fortune on three bulbs and can only claim temporary insanity.) The flowers of Globemaster are sterile, supposedly resulting in a longer show in the garden since they don’t put their energy into seed production after ­pollination. It does make an impressive round umbel the size of a head of iceberg lettuce, studded thickly with rosy purple flowers. The ball balances on a thick stem about 2 feet high.

Drumstick allium, A. sphaerocephalum, is more subtle. I enjoy the maroon-red flower heads, tightly packed into ovals the size of a kiwi fruit, blooming in midsummer. They wave in the breeze on stems 2 to 3 feet long and are particularly delightful when contrasted with gray foliage. I planted them to poke through the arching foliage of the handsome shrub rose Rosa glauca, whose leaves are gray with a maroon ­underside. Native to a valley near Bristol, England, drumstick allium has proved to be one of the most popular and adaptive English plants.

No longer classified as an allium, ­Sicilian onion (Nectaroscordum siculum, formerly A. siculum) grows in the wild from France to Turkey and blooms in May or June. Twenty to 40 inches tall, it has relatively large pendant bells tinged with pale green, ivory, and adobe pink. The flowers are especially effective in large clumps so that their subtle hues are not overlooked. The bulbs take part shade, and the flower heads dry to a golden ivory color.

Scarce as hen’s teeth

The national appetite for ornamental onions continues to grow, but few other species are available commercially. However, specialty plant societies often offer unusual species through seed sales and exchanges. It is worth scouting for seed since most species germinate easily and flower within a few years. Especially worth the search are two stunning blues: A. beesianum, from western China, with drooping royal blue flowers on 6- to 10-inch stems in late summer, and A. cyaneum, also from China, featuring cobalt blue or blue-purple flowers on 4- to 6-inch stems in late summer.

A. narcissiflorum is an exciting species from the Alps. It blooms in summer, bearing nodding, flared pink bells like satin skirts on 6- to 10-inch stems. Though the flowers bear no resemblance to narcissus in form or color, they are very pretty nonetheless and are a natural for the rock garden. So is tiny A. acuminatum, the pink wild onion of the Pacific Northwest. It’s only 3 to 6 inches tall, and its deep lavender-pink flowers appear in spring.

Naples garlic (A. neapolitanum) is native to the Mediterranean region. Its umbels of fragrant, star-shaped white flowers open on 12- to 20-inch stems in spring. A tender bulb performing best in sun and well-drained soil, it’s a good bet for West Coast gardeners. Another good choice for that region is the one-leaf onion (A. unifolium), a native of the coastal mountains. Despite its names, it usually produces two or three thin leaves. It resembles Naples garlic in its culture, height, and flower shape but bears lovely pure pink blossoms in early summer. Both go dormant in midsummer.

It’s difficult to avoid comparing the flower heads of A. schubertii with fireworks. The pedicels of each flower in an umbel are of a different length—some long, some short—with a resulting explosive look. A flower head can measure as much as 10 inches across. The flowers are usually violet, sometimes pink, and appear on stems 1 to 2 feet high. Native to the eastern Mediterranean and North Africa, this exotic-looking allium needs excellent drainage. Its hardiness is still being tested but, once again, West Coast gardeners may have good results.

Design

It takes time to become accustomed to designing with ornamental onions. The clump formers, such as nodding onion and Chinese chives, are the easi­est to work into a border. Since they hold their leaves, they’re as easy as daylilies to position with companion plants.

The drumstick types take some thought to position. They look forlorn and out of place against a backdrop of bare soil. Those naked stems need ­covering. They look silly otherwise. ­Perhaps that was my original complaint with A. giganteum. I had been bombarded by those images of a freaky ­purple lollipop clutched by that ­omnipresent Dutch toddler, and the prejudice that was implanted in my mind has taken time to overcome.

I like to think of myself as broad-minded. I have at times tried many plants that the horticultural establishment viewed as low-brow. Gertrude Jekyll once pointed out that “a geranium was a geranium long before it was a bedding plant.” We can easily develop a bad taste for a plant based strictly on how it has been handled (or mishandled) by someone else. We may dislike it for its Victorian bedding-plant past, for a color we’ve sworn to loathe, or, in my case, for the sins of advertisers. I spent hours this fall trying to ­decide how I could possibly use giant alliums in my border. Finally, I planted a handful behind clary sage and rhubarb. I’ll reserve judgment until they bloom. If worse comes to worst, I’ll eat them.

Sources

The following offer a wide selection of ornamental allium bulbs or plants.
Bear Mountain Alpines, PO Box 2407, Evergreen, CO 80439. Catalog free.
Busse Gardens, 5873 Oliver Ave. SW, Cokato, MN 55321. Catalog $2.
Daffodil Mart, Rt. 3, Box 794, Gloucester, VA 23061. Catalog $1.
Van Engelen, 313 Maple St., Litchfield, CT 06759. Catalog free.
Rob Proctor’s alliums live in Denver, Colorado, where he is an author, an artist, and a gardener extraordinaire.