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Perennial plant of the year – Allium ‘Millenium’

Published December 11, 2017
Allium 'Millenium'
Allium 'Millenium,' courtesy Walters Nursery

URBANA, Ill. – The Perennial Plant Association has awarded the title Perennial Plant of the Year 2018 to Allium ‘Millenium’. This herbaceous perennial, a relative of 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. 

“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 all season long and for its drought-resistant constitution. The spelling, though, raises questions. It is often spelled ‘Millennium’, consistent with the correct spelling for the turn of the century, but was apparently registered under the name ‘Millenium,’” says Martha Smith, University of Illinois Extension horticulture educator.

The genus Allium contains over 900 species of bulbous plants in the Northern Hemisphere, but is perhaps best known for a dozen or so species that compose the culinary vegetables and herbs: onion, garlic, leeks, shallots, scallions, and chives. The genus is also known for a few dozen ornamental flowers 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 once more species are introduced to cultivation. 

Allium ‘Millenium’ has numerous virtues to add to the landscape setting. Growing best in full sun, each bulb typically produces an upright foliage clump of grass-like, glossy deep green leaves reaching 10-15 inches tall in spring. In midsummer, two or three flower scapes appear from each bulb rising above the foliage, with each scape producing two to three showy two-inch spherical umbels of rose-purple florets for up to 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’ doesn’t let the heat bother it. Easily grown in Zones 4-9 (and possibly Zone 3), it makes 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 other than bulb rot, which may occur in wet soils.  In overcrowded growing conditions leaf spot may occur. Deer and rabbits leave ‘Millenium’ alone.  Alliums are sometimes avoided due to their reseeding behavior. Fortunately, ‘Millenium’ exhibits 50 percent reduced seed production, thus less potential for self-sown seedlings.

Allium ‘Millenium’ has true bulbs attached to a short, stout rhizome, forming an ornamental herbaceous clump that is easily propagated by division. Growers can expect a good display with three to five bulbs per one-gallon container. Free draining soil medium and full sun are required.  Once in the garden, ‘Millenium’ can easily be lifted and divided in either spring or fall. Cut back foliage in late fall.

Pollinators will flock to Allium ‘Millenium’. Butterflies and bees will thank you for adding ‘Millenium’ to your garden.  Pair with shorter goldenrods (Solidago sp.) such as ‘Little Lemon’, which reaches one and a half feet tall. Goldenrods are late-summer pollinator magnets that will offer beautiful contrasting golden yellow blooms.

Another late summer re-blooming perennial to consider is Oenothera fremontii ‘Shimmer’ with its low growing, silvery foliage adorned daily with large yellow flowers that open in late afternoon and fade to an apricot color by morning. Being tap-rooted, this evening primrose is well behaved, not creeping through the garden as some rhizomatous spreading evening primrose are infamously known for.

Allium ‘Millenium’ also looks great backed with the silver foliage of Perovskia atriplicifolia, Russian sage, or the native Scutellaria incana, Downy skullcap, with its numerous spikes of blue flowers above trim green foliage. Or simply plant en masse and enjoy the rose-purple display! 

This low-maintenance dependable perennial will not disappoint. Blooming at a time when most of our garden begins to decline in the tired excess of the season, ‘Millenium’ offers much needed color. It is truly an all-season plant offering attractive shiny foliage spring through summer and capping off the season with its crown of perfectly round, rose-purple flower umbels.

News Writer:

University of Illinois Extension