The genus Allium (commonly known as onion) consists of several species that many northern gardeners know well, most commonly chives which have been used for eons in cooking.
But, in recent years, there has been an explosion of ornamental onion cultivars. If you are looking for perennials that truly are easy to grow, this plant is for you. Few perennials are as easy care and beautiful as ornamental onions.
I’d like to highlight three great cultivars that you can easily find at your local garden center. What I really like about these is that you can extend the bloom time in your garden by planting all three and they will bloom one right after the other. I’ll start with the earliest bloomer:
The cultivar ‘Summer Beauty’ has been available for several years and for many gardeners, was the first ornamental onion we put in our perennial gardens. Blooming in midsummer, the foliage looks like chives and the 2-inch round pinkish purple flower heads rise just above the foliage. The flowers are sterile so no worries about invasiveness, which is a problem with some bulbous Allium that are heavy seeders. This variety matures at 12 to 18 inches tall and just a bit wider. It has an upright, vase shape to it.
Allium ‘Millenium’ was the 2018 Perennial Plant Association Plant of the Year and you may have seen lots of promotion about it then. A very heavy bloomer, it starts flowering just as ‘Summer Beauty’ is finishing. The flowers are more of a rosy purple shade and are slightly larger than 2 inches in diameter. It reaches a mature height of 15 to 20 inches and spreads only 10 to 15 inches.
Allium ‘Medusa’ PP28701 is a 2017 introduction. It is one of the last to bloom in summer. Medusa’s foliage is a bit different—it twists and snakes and is a grey-green in color. The name is a shout-out to the mythological Medusa who had snakes for hair. The 2-inch flowers are a light amethyst purple in color. Slightly taller than the others, it can reach a height and spread of 24 inches.
Grow Tips for Ornamental Onions
Truly these plants are easy to grow, almost difficult to kill! They thrive in full sun sites and can tolerate soils that are dry. They will also tolerant salt, making them appropriate for boulevard plantings. They need no extra winter covering in most of Minnesota, as they are hardy to USDA Zone 4. I suspect they may tolerate zone 3 with good snow cover, too. Another benefit: the deer and rabbits just don’t like that onion taste and smell of the foliage, so they stay away. Yet, the plants attract bees, butterflies and other pollinators. And, they make great cut flowers so use them in your summer bouquets. I prefer to cut my Allium back in the spring, leaving the spent flower heads to collect some snow in the winter.
These are just great in a perennial garden and because of their mature size are used in the middle of the garden, just behind the low plants. I love using them in masses of three, five or seven plants to really make an impact. Because of that long strappy foliage, use them in combination with perennials with larger foliage, such as cranesbill.