Allium giganteum, also known as Giant Onion
They look like they’re right out of a Dr. Zeus book — giant purple balls stuck like lollipops on naked green stems. I love to watch the expressions on people’s faces when they encounter the colorful spheres for the very first time. Drought tolerant and virtually disease and pest-free, alliums (also known as ornamental onions) are a sure bet if you’re looking to liven up your garden.
Partly due to the fact that they appear to hover, alliums add a big dose of fun to almost any garden setting. Teeter-tottering above other flowers, their purple flower heads act as key accents throughout the perennial border. In formal gardens, they inject a note of whimsy, while in more informal settings they make a dramatic statement, forming unexpected color combinations with other plants in the garden.
Alliums in a spring garden
We have Rosemary Verey, the famous British gardener, to thank for introducing the world to these beautiful flowers. Her famous Laburnum Arch at Barnsley House is today one of the most iconic garden images. Created in 1964, the design centers on a tunnel of golden chain tree flowers under planted with dense rows of purple alliums. The cascading yellow flowers atop the deep purple floating orbs has been reproduced in one form or another for decades.
Rosemary Verey’s famous Laburnum Walk
The allium family is a genus of flowering plants that has hundreds of species, including onions, garlic, scallions, shallots, leeks and chives. While most have been cultivated for centuries as food crops, the ornamental onions are grown strictly for their decorative qualities. A word of caution, though; the bulbs may look like onions, but they are not edible.
Allium gigantum poking up among pink roses
Since they are spring bloomers, allium bulbs need to be planted in the fall (once the soil has cooled.) I plant mine just after the leaves have fallen. Six months later in late spring, just when you’ve all but forgotten them, basal rosettes with giant, paddle-shaped leaves start tracing patterns on the soil in the garden.
Soon after the leaves appear, the plant sends up a thick, leafless stem at the end of which is a swollen bud. As the bloom takes shape, thousands of tiny, star-like flowers open to form a dense purple ball. Once formed, the flower heads are incredibly long-lasting, retaining their color for a week or more. The flowering stage continues with each plant producing one or two more blooms.
A fully developed flower head
I like to plant alliums in groups of threes or fives and sow them haphazardly throughout the garden. This makes for an abstract design that combines well with both formal and informal spaces. It’s important not to plant the bulbs too close together, though, in case come spring, their spheres collide and ruin the effect.
Alliums look great with other spring flowers like peonies and irises. And the later blooming varieties make stunning companion plants to salvia, yarrow, monarda, catmint and daylilies. Alliums are not repeat bloomers, so after they exhaust themselves, they go dormant for the summer. I plant daylilies by my alliums to hide the foliage once it starts to wither.
Spring color combination with alliums
Alliums flower best in full sun, although they’ll also grow in semi-shade (see above.) Once the flower has died, cut the flower stalk down to refocus energy into the bulb. Dried flower heads make great additions to indoor flower arrangements, by the way.
POPULAR TYPES OF ALLIUMS
There are many different species of alliums, but here are some of the most popular:
Purple Sensation, the earliest bloomer of all the large-flowered alliums. flowers in late spring. It makes a stunning companion to peonies, bearded irises and delphiniums. The 4″ to 6″ diameter violet globes float on sturdy stems that rise to 24″ high.
Allium ‘Purple Sensation’
If you’re looking for a big ‘wow’, try Globemaster and/or Gladiator. The tallest of the ornamental onions, these varieties boast huge purple flower heads (some measuring as big as 8″ to 10″ across) on 3 to 4-foot stems. A white version called Mount Everest is slightly shorter.
Allium ‘Mount Everest’
Adorable Drumstick produces reddish purple cone-shaped flowers (like drumsticks) in July and is a great companion to other summer-blooming plants like daylilies, daisies, and coneflowers.
Star of Persia, Allium Christophii, is a little more wild. It produces star-shaped fuchsia flowers on gray-green stems.
Star of Persia/Allium Christophii
If you’re looking for real fireworks in the garden, try Schubert allium whose pink umbels look like an explosion. Seed heads look great in the garden, too, long after the blooms have faded.
In addition to these great cultivars, there are lesser-known alliums that can keep the blooms going all summer long. For more information on these varieties and a great video on how to plant them, click here for Fine Gardening’s excellent article on these summer beauties.