US: Allium 'Millenium' is the 2018 Perennial Plant of the Year

The Perennial Plant Association has awarded the title Perennial Plant of the Year 2018 to Allium ‘Millenium’. This herbaceous perennial, relative to the common onion, is a workhorse of the late summer garden. Bred by Mark McDonough, horticulture researcher from Massachusetts, ‘Millenium’ was introduced through Plant Delights Nursery in 2000 where it has proven itself year after year earning rave reviews. ‘Millenium’ is spelled with one “n”, as registered, but is sometimes incorrectly listed with two “n”s. This cultivar is the result of a multigenerational breeding program involving Allium nutans and A. lusitanicum (formerly Allium senescens ssp montanum), selected for late flowering with masses of rose-purple blooms, uniform habit with neat shiny green foliage that remains attractive season long, and for its drought-resistant constitution.

Photo Credit: Walters Gardens, Inc.

The genus Allium contains more than 900 species in the northern hemisphere but is perhaps best known for a dozen or so species of culinary vegetables and herbs: onion, garlic, leeks, shallots, scallions, and chives. The genus is also known for a few dozen ornamentals that grow from bulbs and sport tall stems with big globe-shaped blooms in spring. The vast majority of the genus is little known and absent from horticulture, yet possesses significant ornamental potential.

Allium ‘Millenium’ has numerous virtues to add to the landscape setting. Growing best in full sun, each plant typically produces an upright foliage clump of grass-like, glossy deep green leaves reaching 10-15” tall in spring. In midsummer, two to three flower scapes rise above the foliage with each scape producing two or three showy two-inch spherical umbels of rose-purple florets that last as long as four weeks. The flower umbels are completely round (spherical), not domed or hemispherical as they are in some Allium species. They dry to a light tan often holding a blush of their former rose-purple color. While other alliums can look scraggly in the heat of the summer, ‘Millenium’ does not let the heat bother it! Easily grown in zones 4-9 (possibly zone 3) makes it a great perennial in many areas of the country. In very hot summer climates it does appreciate afternoon shade.

No serious pest problems have been reported. Leaf spot may occur in overcrowded growing conditions. Deer and rabbits leave ‘Millenium’ alone. Alliums are sometimes avoided due to their reseeding behavior. Fortunately ‘Millenium’ exhibits 50% reduced seed production, raising less concern for self-sown seedlings.

Allium ‘Millenium’ has a fibrous root structure forming an ornamental herbaceous clump easily propagated by division. Once in the garden, ‘Millenium’ can easily be lifted and divided in either spring or fall. Cut back foliage in late fall.

Photo Credit: Walters Gardens, Inc.

For more information:
Perennial Plant Association
www.perennialplant.org