In late spring and early summer, when they come into flower, allium bulbs make quite the statement in planting beds. Whether they’re mixed with perennials or planted in an area all their own, these onion relatives have so many worthwhile traits. They’re deer resistant, unbothered by rabbits, chipmunks, and squirrels, long-lived, and downright stunning. Alliums come in a surprising array of forms and colors, even though the flowers are always found in clusters atop straight, leafless stems. If you’re looking for the perfect alliums to add to your landscape, this article covers the best varieties for the job.
How to include alliums in your landscape
Like other members of the onion family, which includes chives, shallots, garlic, leeks, and others, alliums are ornamental onions that have a distinctive smell, which is why the critters and insect pests tend to leave them alone. Most of the allium varieties listed below are fully winter hardy even in cold growing zones where temperatures go down to -30 degrees F, making them a great fit for most gardens. However, the bulbs need to pass through a period of cold winter weather (10 to 12 weeks at or below 40 degrees F) in order to initiate blooms, so alliums are not appropriate for warm-climate gardens. They do best in cool to cold hardiness zone regions.
Though you can plant allium bulbs in a straight line, like little soldiers in a row, for the best visual effect and the most natural appearance, plant the bulbs in casual groups or clusters of 5 to 9 bulbs. Keep the allium bulbs in each group 4 to 6 inches away from each other to give each one plenty of room to grow. You can dig one large hole that’s big enough to accommodate an entire group of bulbs, or dig a series of smaller holes and plant each bulb in the group individually. Either way, the results are the same.
I love tucking clusters of alliums in between the perennials in the full sun bed along my driveway. They’re up and flowering before the perennials like iris and peony reach their peak, adding another layer of interest to the garden. Then, after the blooms fade, the starburst-like seed heads continue the show.
How deep to plant alliums
Allium bulbs should be planted to a depth equal to two-and-a-half times the diameter of the bulb. That means smaller species may only need a plant depth of 3 or 4 inches, while allium varieties with larger bulbs have to be planted much deeper. Good drainage is key.
When to plant allium bulbs
It’s important to know the best time to plant alliums, too. Like other spring-flowering bulbs, such as daffodils and tulips, alliums are planted in the autumn. The increased rainfall and cooler air temperatures, combined with the still-warm soil, give the bulbs plenty of time to form roots before the ground freezes.
Mulch newly planted allium bulbs with three inches of shredded leaves, bark, or compost to insulate them through the winter months if you live in a very cold climate. I skip this step in my Pennsylvania gardens with no negative consequences.
Now that you know how to plant these wonderful bulbs, let me introduce you to some top-notch allium varieties.
The best varieties of alliums for home gardens
This allium variety is a real a firework of the garden. Each individual bloom in the cluster is on a different length flower stem, resulting in a burst of multi-level blooms on top of the stem. Looser and airier than some other types of alliums, A. schubertii is perfect for naturalistic gardens and to tuck in among ornamental grasses.
Allium bulgaricum (A. siculum)
Among the most unusual alliums, this selection has large, bell-shaped flowers. The stems are tall and straight, while the flowers are nodding and bi-colored. A welcome sight to spring pollinators, A. bulgaricum’s blooms don’t last as long as some other types, but they are oh so lovely!
‘Globemaster’ earns its name by producing tight, round flower clusters on straight-as-a-line stems. They’re quite tall, reaching 2 to 3 feet in height. Like all alliums, they make terrific, long lasting cut flowers, and even after the flowers are spent, the interesting seedpods hang around in the garden for a long time. ‘Globemaster’ is arguably the most well-known variety of allium. I have many of them in my front garden, and they return reliably year after year. They were planted 10 years ago.
With luscious pink-purple blooms, A. giganteum is at home in any type of garden. The large flower clusters are perched on 3 foot-tall stems. In my garden, I have the bulbs tucked into a stand of Golden Alexanders (Zizia aurea) and they always manage to bloom simultaneously, creating quite a display. The bees adore all alliums and occasionally I spy an early season butterfly feeding on them, too.
Known as drumstick allium, the flower head of this allium bulb is tight as a drum. It’s bright magenta on top and green below. The individual flowers open in succession, from the top of the cluster down. Each globe is only an inch or so across, and the stems are slender but strong. Drumstick alliums wobble in the breeze. Plant this beauty in large drifts for the best results. As you can see, I’m very fond of this allium bulb when it’s planted with the color orange. Calendulas, geraniums, and celosia are great partners. It’s much later blooming than other types of alliums, so it it’s in its prime right along with the annuals.
An early blooming, petite delight, Allium caeruleum is the loveliest sky blue. Standing at just 10 to 12 inches tall, this little cutie is best appreciated when planted at the top of a retaining wall or someplace where you can view it at eye-level. The ball-like flower cluster is an inch across. It’s a favorite of many of our smaller bee species, though the honeybees adore it, too.
The leaves of these alliums are wide, smooth, and fleshy, unlike most other species. They also have a grey-blue coloration. And, the flowers are white and very short stemmed. Standing at just six inches tall, A. karataviense may not be as visually eye-catching as some other choices, but it sure does grab your attention simply because it’s so unique. Be sure to plant it next to a walk or in another high-traffic location.
Each large, round flower cluster of this allium cultivar consists of hundreds of six-petaled flowers, each shaped like a slender starfish. The stems are around 18 inches tall and the leaves are medium green and strap-like. Since each individual flower sits at a slightly different level, Allium christophii is a little less “ball-like” than some other varieties. The grouping shown in this photo is planted in my front garden, between the larkspur and Heliopsis plants.
Mixing and matching different types of alliums
Don’t be afraid to experiment with combinations of different allium varieties planted together in the same area. Each one has a slightly different bloom time, height, and flower color, resulting in some pretty spectacular combos.
As you can see, there are so many different types of alliums worth including in your garden. Plant some this fall. Come next spring, I guarantee you’ll be happy you did.
Do you grow alliums? We’d love to hear about your experience with them in the comment section below.
For more on growing great bulbs, please visit the following articles:
- Unusual flower bulbs
- Deer-resistant bulbs for a spring show
- Squirrel-proof bulbs
- The best lily bulbs for your garden
- How to keep winter paperwhite bulbs upright