By Robin Portelli, Cornwall Master Gardener Volunteer
This article appeared in the July 2021 Issue of Gardening in Orange County.
Alliums, otherwise known as ornamental onions, literally can be seen popping-up in sunny gardens around the area. The most common varieties bloom in late spring to early summer but there are some late summer to fall bloomers as well. Most of them will have fragrant showy globe-like flower heads on a single stem. These perennial bulbs do well in USDA Hardiness Zones 3-9 depending on the variety/cultivar. Well drained soil is important since many of the bulbs are large and will rot if they sit in too much moisture. Their heights range from 12-48 inches. Some of their attributes include being deer, rabbit and vole resistant along with being pollinator friendly attracting bees, butterflies and occasionally a hummingbird. Plus, they come in a variety of eye-catching colors including purple, pink, blue, white, and yellow.
My favorite is one of the largest most popular varieties, Allium giganteum. In June, it gets 4 feet tall with beautiful, round softball size, lavender, umbel type flower heads. I have them interspersed in my perennial garden bed. Since their leaves die back before they bloom, I have the base of the plant covered by other plants. Even after it blooms, the dried flowerhead remains an ornamental feature for most of the summer.
Another favorite of many gardeners is Allium schubertii. Even though it only grows to be 16-20 inches tall, its flower diameter is 12-15 inches! People state it looks like “an explosion of rosy florets caught in mid-air” or “like a colorful pinkish tumbleweed.” This variety can tolerate part shade but prefers full sun like most alliums. It is suggested to be used in naturalistic gardens. I planted this bulb in the fall for the first time. We shall see if it lives up to all the hype.
If you are looking for a true summer blooming allium, you may want to consider the ‘Millenium’ hybrid as your first choice. It was the Perennial Plant Association 2018 Plant of the Year. It is smaller, growing to a height of 15 inches, but it is clump forming with many purplish-pink long-lasting blooms. The foliage is described as glossy, deep green with an ornamental grass-like appearance. It is very heat tolerant. The dried brown flowers seem to last thru ought the winter.
A Northeast U.S native ornamental onion is Allium cernuum . It is known as the nodding onion. It can be found in woods, prairies, bluff edges and dry meadows from New York to Michigan into Canada. It is another clump forming allium that grows 8-18 inches tall. It has summer blooming light pink to lavender drooping flowers. Native Americans used the bulbs for medicinal purposes. As other alliums, it attracts many bees and butterflies. It can be a great addition to a rock garden but be cautious. It can self-seed so gardeners are advised to cut off the seed heads after it blooms.
There are many other allium varieties waiting for you to research and hopefully pick for your own garden. The larger varieties are truly a festive sight to see.