Alan is the Director of Horticulture at Powell Gardens and author of The Gardener’s Butterfly Book. He holds a bachelor’s degree and master’s degree in landscape architecture from Iowa State University and Louisiana State University, respectively, specializes in garden design and maintenance, and has supervised and designed dozens of landscaping projects. A member of the American Public Gardens Association, Alan plays a key role in Powell Gardens, one of the largest botanical gardens in Missouri. The garden boasts world-class architecture and more than 17,000 accessions of plant displays that capture the essence of the American Midwest.

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Alliums for All
by Alan Branhagen       #Flowers   #Purple   #White

Alliums or ‘ornamental onions’ come in all sizes and colors—from giant globe-shaped purple spheres to delicate yellow sprays. The best part is that deer, squirrels, voles and rabbits find them foul-tasting. Here are some awe-inspiring alliums to add to your garden this year.

Allium ‘Purple Sensation’ makes a dramatic mass in late spring.
(Foreground is waning Narcissus triandrus ‘Stint’.)

Alliums (aka “ornamental onions”) comprise a marvelous group of plants in the lily family always underutilized by gardeners. From Allium aflatunense to Allium zebdanense (literally from A to Z), most don’t have common names but there is an allium for all. Allium’s various forms from bodacious and big to shade-loving delicacies make them valued by gardeners in any venue. The giant globe-shaped flowering types are whimsical and fun while the shade-loving species are delicate and sublime. Their flowers’ colors range from lavenders and purples to pink, yellow, blue, burgundy and white. As they are in the same genus as the culinary onion, they contain the same properties that make them unpalatable to garden pests like deer, squirrels and voles.

Allium christophii.

Allium schubertii.

Allium giganteum

Allium atropurpureum.

For fabulous spherical flower forms in late spring to early summer there are four violet-hued classics: from volleyball-sized Allium schubertii to softball-sized Allium giganteum and A. christophii to baseball-sized Allium aflatunense. Hybrids between these sport an intermediate set of flowers in all sizes in between. King of the group is the aptly named Allium giganteum whose lilac-purple flowers tower atop a 4-foot, yet sturdy, stem (flowers are white in the cultivar ‘White Giant’). Next in height is the Allium aflatunense: usually represented by the cultivar ‘Purple Sensation’. This allium grows to about 30 inches tall and the flowers are a gorgeous violet-purple. Both these dramatic alliums bring early season flower height to any border. Allium christophii grows to about 20 inches and the flowers are unique silvery-lavender that is simply spectacular. It is low enough and open enough that it actually looks great mixing and mingling with neighboring flowers or foliage of the season. Allium schubertii must be seen to be believed with its huge, open explosion of flowers no more than 2 feet tall. It can gracefully burst through neighboring flowers and foliage as well. Let the flowers of all these go to seed in the garden as the seed heads retain the marvelous form of the flowers and dry beautifully. I have witnessed them tactfully spray painted to enliven the color of a garden well into summer. Dried and used indoors they are everlasting.

Another foursome of alliums blooming at the same time (late spring into early summer) offer a cool range of colors on plants that grow from 12 to 24 inches tall for the most part. They can be grown beneath the above but also as complements to popular peonies or Siberian iris. The smallest is the Allium roseum with lovely pink umbels reaching 12 to18 inches. Next in the 1- to 2-foot range is Allium atropurpureum whose flower is best described as a deep burgundy—suitable for a “black” border and a lively contrast with the rest. In the same height range is the true-blue-flowering Allium caeruleum, which often attracts early butterflies and makes a great choice for a blue or blue-and-yellow border. Tallest of this bunch is the Allium nigrum (18 to 30 inches) with silvery off-white flowers—each floret containing a green stripe down the petal. I have seen it in beautiful contrast planted with Allium atropurpureum.

Two alliums bloom in yellow on no more than 1-foot-high stems but they are very different from each other. In late spring the sparkling yellow Allium moly boasts golf-ball-sized bright yellow flowers in an up-facing umbel. The other yellow-bloomer is Allium flavum whose flower is more of a firework explosion of mostly pendulous florets but it doesn’t bloom until later, near midsummer.

If you have a shade garden there are also some alliums that will work for you and mingle in well with other moist woodland wildflowers and traditional shade plants like hostas. These are all short with roughly golf-ball-sized flower clusters. First is the native Allium tricoccum aka wild leeks, which are mainly grown for their broad and lovely ephemeral leaves that emerge in early spring. The greenish-white flowers are hardly noticed on naked stems in midsummer after the leaves have long gone and produce neat black seeds that burst from each flower’s capsule. Allium triquetrum also does best in at least partial shade and blooms in late spring. It has drooping, bell-flared flowers of white with a light blue stripe down each petal. My absolute favorite is the hard-to-find but worthwhile Allium zebdanense with pristine white pendant flowers on stems so fine the flowers always tremble in the slightest breeze. Delightful nodding wild onion (Allium cernuum) also thrives in open shade and is valued for its late summer bloom of nodding pink flowers. Allium cernuum will also grow in full sun in moist soils and is the “stinking onion” namesake flower of Chicago though the plant, like all alliums, must be crushed to release the oniony aroma.

Allium zebdanense.

The foliage of Allium tricoccum.

When you thought all the alliums were done flowering there is another hurrah starting around Labor Day when two lovely alliums bloom: prairie onion (Allium stellatum) and garlic chives (Allium tuberosum). Allium stellatum prefers full sun and has numerous 2-foot stems topped by 3-inch balls of rosy pink flowers that are always a star of the fall garden. I like to plant it with blazingstars (Liatris scariosa) and early flowering asters like Aster laevis. Garlic chives are a magnificent herb but really ornamental for its late-season white flower umbels that attract hoards of beneficial insects including bees and butterflies to a garden. Garlic chives are a profuse self-sower so I always deadhead all the flowers to prevent seeding. The allium finale is the diminutive but delightful Allium thunbergii ‘Ozawa’ with lavender pink flowers atop 1-foot-high stems in October or later.

Allium tuberosum attracts a wealth of beneficial insects and butterflies (Viceroy shown here).

I left out some actual edible onions (Allium cepa), scallions (Allium fistulosum), chives (Allium schoenoprasumf) and garlic (Allium sativum). The first two are best left to edible landscapes but chives make a nice late-spring bloomer as long as you deadhead them to prevent seeding. Some garlic varieties have spectacular growth forms in elegant spirals and should be considered for ornamental use too.

All in all the alliums A to Z are a beautiful garden addition most notably for their architectural spherical flower heads that create a contrasting dimension in any garden.


(From State-by-State Gardening March/April 2012. Photography by Alan Branhagen.)


Posted: 05/09/12   RSS | Print


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