Perennial Plant of the Year 2018

Gardeners Resources, Perennial of the Year

Each year, members of the Perennial Plant Association from all across North America vote on their choice for Perennial Plant of the Year™

Their pick for 2018 is Allium ‘Millenium’



USDA Zones 3 or 4 to 9


Allium ‘Millenium’ grows best in full sun. In very hot climates partial shade may be best.


Grows best in well-drained soils.


Allium ‘Millenium’ is a perfect selection for full-sun gardens where its sleek structure can complement many other growth habits. Cut flowers retain a blush of their summer color.

Unique Qualities 

Allium ‘Millenium’ is a butterfly magnet. The plant is interesting through multiple seasons for both foliage and large, gorgeous blooms. Reseeding is much less a problem than in other alliums.


Allium ‘Millenium’ is subject to no serious insect or disease problems. Deer and rabbits usually avoid ‘Millenium’.

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 occasionally 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.


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.


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’ that 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 companion perennial to consider is Oenothera fremontii ‘Shimmer’ with its low-growing silvery foliage adorned daily with large yellow flowers that open late afternoon and fade to an apricot color by morning. Being tap-rooted this evening primrose is well behaved, not creeping through the garden, for which, rhizomatous spreading evening primroses are famously known. Allium ‘Millenium’ 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 ‘Millenium’ 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 that offers attractive shiny foliage spring through summer and caps off the season with its crown of perfectly round rose-purple flower umbels!

Martha A. Smith, Horticulture Educator, University of Illinois Extension

Mark McDonough, Plant breeder/horticulture researcher, Massachusetts

Information from the Perennial Plant Association website

Past Perennial Plant of the Year selections are as follows:

2017 – Butterfly Weed (Asclepias tuberosa) 
2016 – Japanese Anemone (Anemone ‘Honorine Jobert)
2015 – Dwarf Cranesbill (Geranium ‘Biokovo’)
2014 – Tall Switch Grass (Panicum virgatum ‘Northwind’)
2013 – Japanese Solomon’s Seal (Polygonatum odoratum ‘Variegatum’)
2012 – Siberian Bugloss (Brunnera macrophylla ‘Jack Frost’)
2011 – Arkansas Blue Star (Amsonia hubrichtii)
2010 – Blue False Indigo (Baptisia australis)
2009 – Japanese Forest Grass (Hakonechloa macro ‘Aureola’)
2008 – Cranesbill Geranium (Geranium ‘Rozanne’)
2007 – Blue Catmint (Nepeta racemosa ‘Walker’s Low’)
2006 – Border Pink (Dianthus Firewitch)
2005 – Lenten Rose (Helleborus x hybridus mixture)
2004 – Japanese Painted Fern (Athyrium niponicum var. pictum)
2003 – Shasta Daisy (Leucanthemum x superbum ‘Becky’)
2002 – Summer Phlox (Phlox paniculata ‘David’)
2001 – Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’)
2000 – Dwarf Pincushion Flower (Scabiosa columbaria ‘Butterfly Blue’)
1999 – Golsturm Coneflower (Rudbeckia fulgida ‘Goldsturm’)
1998 – Purple Coneflower (Echinacea purpurea ‘Magnus’)
1997 – Perennial Salvia (Salvia x sylvestris May Night)
1996 – Beard-tongue (Penstemon digitalis ‘Husker Red’)
1995 – Russian Sage (Perovskia atriplicifolia)
1994 – Dwarf Astilbe (Astilbe simplicifolia ‘Sprite’)
1993 – Hybrid Speedwell (Veronica ‘Sunny Border Blue’)
1992 – Threadleaf Coreopsis (Coreopsis verticillata ‘Moonbeam’)
1991 – Palace Purple Coral Bells (Heuchera micrantha ‘Palace Purple’)
1990 – Creeping Woodland Phlox (Phlox stolonifera)