University of Vermont
Summer News Article
Department of Plant and Soil Science
PERENNIAL PLANT FEATURE: ALLIUMS
Leonard Perry, Horticulture Professor
University of Vermont
Alliums (said as al-e-UMS) are often known as ornamental or flowering
onions, yet this name doesn’t really do justice to this easy-to-grow, hardy,
perennial grown from bulbs. This was the first year that the National
Garden Bureau named a Bulb of the Year, and the winner was the ornamental
Ornamental alliums, as contrasted to their vegetable kin (onions, leeks,
garlic and chives to name a few), are grown for their usually globe-shaped
flowers, made up of many individual star-shaped florets. These are
atop stems that arise from a basal clump of leaves, ranging from wide to
narrow depending on the species. Leaves of many go dormant later in
summer when perennials take over the show.
Allium stems can range from one to five feet high, again depending on the
species or cultivar (cultivated variety). Most are grown from bulbs,
ordered from spring until fall, and planted in the fall for bloom the
following season. The widest selection is usually found in catalogs
and online. Depending on species, bloom time can range from early
summer to fall.
The showiest and perhaps most popular, and most often seen alliums, are
those with large flowers, 5 to 10 inches wide on stems 2 to 4 feet
high. The aster-violet ‘Globemaster’ and lavender-blue ‘Gladiator’
bloom in late spring to early summer, after the daffodils and tulips.
‘Stratos’ is similar to ‘Gladiator’, only with slightly larger and paler
flowers. These all combine well with bearded and Siberian iris.
When planting, space bulbs 8 to 10 inches apart, and plant 6 to 8 inches
deep with the pointed side up. ‘Ambassador’ is similar, blooming just
after these though, and with rich purple flowers.
The first to bloom though, before these larger ones, is the most widely
planted allium ‘Purple Sensation’. Its raspberry-purple softball-sized
flower heads are on stems 2 feet or so tall. Blooming about the same
time as ‘Purple Sensation’, with similar size flowers and nice combined with
it, is the white ‘Mount Everest’. Consider combining these with
Also blooming about the same time in early spring is the golden garlic or
lily leek (Allium moly) with golden, starry flowers in clusters atop
one foot stems. Or combine it with the cultivar ‘Powder Puff’, having
large lavender-purple globes on stems about one and one-half foot high.
One of my favorite alliums, blooming in late spring, is the tumbleweed or
Schubert flowering onion (Allium schubertii). Flowers are
fist-sized, rose-purple, and with a unique shape—a spidery, wide oval with
individual floret stalks of unequal lengths—similar to an exploding
fireworks. This heirloom dating to 1843 gets one to two feet high. Plant one
bulb per square foot. Similar is ‘Spider’, only blooming mid-summer
with deeper violet flowers, and the less hardy (USDA zone 5 minimum) Stars
Much smaller flowers, only one inch across and a unique clear blue, are held
one foot or more high on the heirloom blue globe onion (Allium caeruleum).
Space these about 3 inches apart when planting. They contrast nicely
in many areas with early peonies. The nodding onion (Allium cernuum)
also blooms early summer, its unique dainty pink flowers nodding or hanging
down. It is one of about 100 species of alliums native to North America.
Blooming later—late June in many areas—is the drumstick allium (Allium
sphaerocephalon). The wine-colored egg-shaped flower heads,
resembling drum sticks, are produced on two foot high wiry stems. This
heirloom, dating back to 1594, contrasts nicely with many lilies and early
Also appearing in late June, and often lasting until August, is the new
cultivar ‘Summer Drummer’. Its purple and white globe flowers, the
size of grapefruits, are held on stems 4 feet or more high. Interplant
this with daylilies, ornamental grasses, or perennial geraniums.
Slightly lower in mid-summer, with pink flowers, is ‘Pink Jewel’. Even
lower—about one foot high—is the yellow allium (Allium flavum). You
may find several other good mid-summer blooming alliums such as the purple
‘Millenium’ or the light pink ‘Sugar Melt’. Use caution with both the
yellow and Moly onions, which can self-seed prolifically and are even
invasive in some areas.
For an unusual effect, ‘Hair’ allium has tentacle-like green flowers at all
angles from a rosy base. Circle onion is so called from its twisted
blue-green leaves giving a corkscrew effect, from which the deep pink
For late summer, garlic chives (Allium tuberosum) is at home both in
the herb garden, and as an ornamental for its pure white flowers under two
feet high. ‘Ozawa’ Japanese onion begins blooming in September when
the bees are looking for blooms. The orchid pink flowers are held
under two feet high.
These are a few of the more popular ornamental alliums, depicting a range of
heights, colors, and bloom times. Most are hardy to USDA zone 4 (minus
20 to 30 Fahrenheit winter minimum temperature), and are drought
tolerant. They’ll grow in most soils, as long as soils are
well-drained. They prefer, and bloom best, in full sun.
Fertilize on top of the soil after planting and each year as shoots
emerge. Use an organic fertilizer, or one formulated just for
Alliums have few, if any, problems bothering them, including deer and
rodents who don’t like the taste of onions. Consider alliums, too, not just
for gardens but for cut and dried flowers.
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