Having A Ball With Alliums (Ornamental Onions)

They look like they jumped out of a Dr. Zeus book — giant purple balls stuck like lollipops on long flexible stems. Alliums can be startling the first time you encounter them. But there’s so much to love about these drought tolerant plants, including long bloom period and resistance to most pests and diseases. And their whimsical appeal can sure liven up a garden.

BALLS OF FUN

Indeed, alliums bring a daily dose of fun to almost any garden setting. Teeter-tottering over other flowers, their purple flower heads appear to dance across the surface. In formal gardens, they inject a note of humor, while in more informal settings they make a striking statement. And every year as their numbers grow, they form new, unexpected color combinations with other plants in the garden.

Alliums in one of my spring gardens

Ornamental onions as a garden feature were virtually unheard of until Rosemary Verey, the famous British writer and gardener, used them in one of her designs. Her Laburnum Arch at Barnsley House is today one of the most iconic garden images. Created in 1964, the arch features cascading golden chain tree flowers underplanted with dense groups of purple alliums. The jaw-dropping combination has inspired countless similar designs for decades.

Rosemary Verey’s famous Laburnum Walk

ABOUT ALLIUMS

The allium family is a genus of flowering plants that has hundreds of species, including onions, garlic, scallions, shallots, leeks and chives. While most are cultivated as food crops, ornamental onions are grown strictly for their decorative qualities. The bulbs may look like ordinary onions, but they are not edible.

Allium gigantum poking up among pink roses

Allium bulbs are planted in the fall, at the same time as daffodils and tulips. I plant mine just after the leaves have fallen. Six months later, just when I’ve all but forgotten them, giant, paddle-shaped leaves start tracing patterns on the soil surface.

Following the appearance of the leaves, the bulb sends up a thick, leafless stem terminating in a single, swollen bud. As the bloom slowly takes shape, thousands of tiny, star-like flowers combine to form a dense purple ball. Once formed, the flower head retains its color for weeks. And the flowering stage continues, with each plant producing one or two additional blooms.

A fully developed flower head

DESIGNING WITH ALLIUMS

When it comes to designing with alliums, I say do like Rosemary Verey and go big. For the most impact, I plant my ornamental onions in groups of threes or fives and sow them haphazardly throughout the garden. This makes for an abstract design that works well in both formal and informal settings. 

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. After the spring species (like Globemaster) exhaust themselves, though, they go dormant for the summer. So consider planting similarly-leaved plant like daylilies to hide their foliage.

One of my designs combining alliums with pink azaleas and green hostas 

All allium varieties flower best in full sun, although they’ll also grow in semi-shade (see above.) Once the flower has died, cut the stalk down to refocus energy back into the bulb. Dried flower heads make great additions to indoor flower arrangements, by the way.

POPULAR ALLIUM VARIETIES

There are many different varieties 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. The variety makes a stunning companion to peonies, bearded irises and delphiniums. The 4″ to 6″ diameter violet globes float on sturdy stems that grow to 24″ high.

 ‘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.

‘Globemaster’

‘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.

‘Drumstick’ 

Star of Persia (Allium christophii) is a wild-looking allium variety. It produces star-shaped fuchsia flowers on gray-green stems and blooms late spring to early summer.

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. Blooms late spring to early summer.

Allium Schubertii

In addition to these great cultivars, there are lesser-known allium varieties that can keep the blooms going all through the summer. For more information on these as well as a great video on how to plant them, click here for Fine Gardening’s excellent article on these summer beauties.

 

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