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Best Alliums for Flowers and Tips for Growing Them

Ornamental alliums are enjoying a surge in popularity, and it’s no wonder. These gorgeous plants easily meet the top requirements of gardeners across the country: drought tolerance, deer resistance and pollinator appeal.

'Globemaster' allium grows from a bulb planted in fall. It blooms in late spring.

'Globemaster' allium grows from a bulb planted in fall. It blooms in late spring.

Alliums are on the short list of plants deer and insect pests tend to avoid. The plants seem odorless, but step or chew on them and their cell walls break, releasing volatile, sulfur-based chemical compounds with a pungent odor and bitter taste. This makes alliums virtually bulletproof. Though the foliage repels, the flowers offer sweet nectar that’s highly attractive to honeybees, bumblebees and other pollinators.

Many garden alliums are native to mountainous regions in Central Asia, where winters are cold, summers are hot and the soils are thin and porous. This gives them a tolerance, or even a preference, for dry growing conditions—ideal credentials for today’s water conscious landscaping. They are ideal companions for ornamental grasses and other low-maintenance perennials such as sedum, rudbeckia, echincacea and salvia.

Like their culinary relatives, garlic and shallots, most alliums grow from bulbs. Planted in fall, they bloom from late spring to early summer.

The best alliums are also the showiest: big-headed ‘Gladiator’ and ‘Globemaster’ and the widely planted A. aflatunense ‘Purple Sensation’, which is also the earliest bloomer. Its 3-inch diameter, raspberry-purple flower heads stand on 24- to 30-inch stems, last last for up to two weeks and make excellent cut flowers.

Blooming just after ‘Purple Sensation’ are ‘Gladiator’, ‘His Excellency’ and ‘Globemaster’. With blossoms that measure five to ten inches across on three- to four-foot stems, these alliums make a big impression. Their large seed heads look attractive long after the color is gone.

Several other fall-planted alliums deserve mention. Elegant ‘Mount Everest’ has pure white, five-inch flowers. Along with the misleadingly named black onion (A. nigrum) it’s a must-have for any all-white garden. Possibly the most unusual-looking allium is the tumbleweed onion (A. schubertii), with flower heads that look like they were caught mid-explosion. Three equally appealing species are the maroon A. atropurpureum, star of Persia (A. christophii) and the two-tone drumstick allium (A. sphaerocephalon).

'Millenium' is a clump-forming allium that blooms in later summer, with small but profuse flowers.

'Millenium' is a clump-forming allium that blooms in later summer, with small but profuse flowers.

Ornamental alliums that grow from bulbs may produce the most dramatic flowers, but small-headed alliums have their own appeal. These plants emerge from a dense clump of roots and offer foliage that stays green and lush all season long. Bloom time for these non-bulb alliums starts in early summer and, depending on the species, can extend right through October.

One of the best allliums that forms a clump is ‘Millenium’, a hybrid of A. nutans, or Siberian chives. The purple, two-inch-round flowers bloom in midsummer on stiff, fifteen-inch stems that rise above a tidy clump of foliage. The weeks-long blossoms are excellent for cutting. Two other summer bloomers are ‘Sugar Melt’, with light pink flowers, and ‘Summer Beauty’, in lavender-pink.

For a late summer star, look to A. tuberosum. In herb gardens this edible is known as garlic chives, but its pure white flowers on 20-inch stems easily recommend it for the flower border. Allium thunbergii ‘Ozawa’ is the last allium of the season, with orchid-pink flowers that serve as an important nectar source for pollinators that are still foraging in late fall.

Alliums are tough, cold-tolerant plants, and most will grow in USDA Hardiness Zones 3 to 9. As a general rule, they are not fussy about soil, although the ones with large bulbs require good drainage. They are also practically immune to disease and insect problems, and rodents and deer rarely bother them.

Ornamental alliums that grow from bulbs should be planted in fall. Like other fall-planted flower bulbs, they look best planted in groups. The smaller the bulb, the more you should plant in each group. That said, the bulbs can be tucked in almost anywhere, because their foliage will die back a couple weeks after they flower. In fact, it’s best to have other plants nearby to help cover the fading foliage.

The clump-forming alliums can be planted any time during the growing season. They are easy to divide and they don’t mind being transplanted, so they make good pass-along plants. You can keep these plants looking tidy and minimize self-sowing by cutting off the flower stalks after they finish blooming.

Kathleen LaLiberté writes and gardens at her home in Vermont. This article is shared as a service of the National Garden Bureau. 'Millennium' image courtesy of Walters Gardens.