Allium, the same plant family that contains onion, garlic, shallots and chives, also contains many ornamental species, many of which are hardy in Nebraska.  Alliums have long strap-like leaves with beautiful blooms, made up of many small flowers forming a lilac-blue globe, perched atop a tall stalk.  These striking plants range in size from 2-3 inches for A. circinatum to four feet for A. giganteum.  Most Alliums have blue flowers, but species can be found with white, pink, mauve, yellow and greenish flowers. 

The majority of Alliums should be planted in the fall, in full sun with well-drained soil.  The planting depth is approximately 3 times the width of the bulb.  When using these plants in the landscape, remember that Allium foliage dies back after, or sometimes before, the flowers bloom and can leave large holes in the perennial garden if planted by themselves.  Instead, locate Alliums among other plants so that the bare spots are camouflaged when the plants have finished blooming.  Both of the following Alliums are hardy to Zone 4, although plantings in Zones 4 and 5 should be mulched to provide extra winter protection.

Downy Onion or Star of Persia, A. christophii, although one of the shorter species reaching only 15-24 inches in height, it is one of the largest flowered Alliums.  The blooms are made up of many star-shaped, violet flowers forming a globe-shaped bloom, often 10-12 inches in diameter.  The leaves of this species die back before the flowers are fully open.  ‘Globemaster’, a hybrid cross of A. christophii and A. macleanii, is according to Allan Armitage, author of ‘Herbaceous Perennial Plants’ and noted expert of perennial plants, ‘. . .the best ornamental onion I have ever tried.’  Its flowers are deep lavendar, forming 4-6 inch wide blooms; the flower stems are very strong and self-supporting.  The blooms continue to be showy over many weeks, and even have ornamental value after the seed heads have formed.

Giant Onion, A. giganteum, is the tallest species of Allium as you can tell from the common name.  The gray-green foliage emerges in spring followed by a 3-4 foot tall flower stalk topped by many small, lilac flowers.  The densely packed blooms reach 4 inches in diameter; an excellent late spring or early summer bloomer for the back of a perennial garden.  Giant Onion bulbs can be pricey, but will make a spectacular display in the garden.  Plant bulbs in odd-numbered groupings for the best effect; single bulb plantings are less effective.

Many more great ornamental onions are available, including A. stellatum, Pink Prairie Onion; A. schoenoprasum ‘Forescate’, resembling a rosy-pink flowered chive; and A. flavum a yellow-flowered species.  A.  karataviense, Turkistan Onion, is grown as much for the thick, gray-green leaves mottled with purple as for the silver-lilac flowers.  Its dense blooms are 6-8 inches across, rivaling those of Downy Onion.