Alliums: Onion’s pretty cousins

COLUMBIA, Mo. – While you’re familiar with onions, garlic, leeks and shallots, which are all members of the genus Allium, there’s a whole group in that genus that are known for their looks rather than their taste. They’re called ornamental onions or alliums.

These striking members of the amaryllis family produce a long, leafless flowering stalk, or scape, topped with a ball-like bloom made up of a cluster of florets. In the garden, they appear to hover above surrounding plants.

“This is especially true for giant allium. It bears a bloom that approaches 6 to 8 inches in diameter and is held 3 to 4 feet above its leaves,” said David Trinklein, horticulture specialist for University of Missouri Extension.

One of the best allium cultivars is a hybrid called Millennium, Trinklein says.

“It produces an abundance of rose-purple flowers that are about 2 to 3 inches in diameter,” he said.

Each floret is filled with sweet nectar, which invites bees and other pollinators to come and join the party. If you’re interested in attracting pollinators, alliums should be a part of your perennial garden.

While the florets may be sweet, the rest of the plant is not.

“Alliums all have one thing in common. They all have pungent, sulfur-containing compounds known as alliins in their leaves and bulbs,” Trinklein said.

Undisturbed, alliums are relatively odorless in the garden. But step or chew on them and those volatile sulfide compounds are released. The “oniony” smell and strong taste will make deer, rodents and insects give allium a wide berth in the garden.

“They represent some of the most critter-resistant plants available to gardeners,” Trinklein said.

If you want to eat from your garden, chives are both decorative and edible.

“They’re quite attractive in appearance. Chives produce an even smaller flower head, maybe an inch in diameter,” Trinklein said. “Whereas Millennium was bred to be very floriferous, chives were bred to be very flavorful and the bloom is just an added benefit.”

You can purchase alliums as dormant bulbs or started plants. They are most readily available in the spring, although dormant bulbs can be planted in the fall.

As perennials, alliums can handle cooler weather, but they must have well-drained soil. “We most often lose bulb plants such as alliums during the winter. Not from cold temperatures, but from poor drainage,” he said.

Typical clay soils found in Missouri would need to be amended before planting alliums. Trinklein recommends incorporating well-decomposed organic matter into the soil, which he says is a great way to improve a soil’s drainage.

Alliums are considered low-maintenance plants. They are fairly drought-resistant and relatively free from pests, Trinklein said.

The National Garden Bureau has chosen allium as its flowering bulb plant for 2016. If you’re interested in adding allium to your perennial garden, you have many to choose from. Allium comes in a variety of flower sizes, heights and colors, which range from white to purple to blue to yellow. You could easily plant different allium species and create a succession of color in the garden, Trinklein said.