How to Grow Allium
If you want to look like you’ve taken your garden to the next level of design, ornamental alliums are the answer. Planting a few bulbs in the fall will create a mini-sculpture garden in the spring that will not only last while the flowers are fresh, but continue into summer as the flowers dry in place. The single globes float above the surrounding garden and are made up of tiny, individual flowers on thin, hollow stems.
They’re easy, very hardy, and with basal (ground level) foliage that is rapidly covered by other growing perennials, you won’t face the “what to do with yellowing leaves” issue that accompanies most other bulb plantings.
You can find ornamental allium in many different shades of purple, pink, red, blue and white, and in sizes that range from “wow!” to “ahh…how sweet!” Used to accent developing foliage of later bloomers, or provide the finishing architectural touch to a bed of spring favorites, allium will give your garden the professional touch you’re striving for.
When & Where to Plant Allium
Don’t make the mistake of digging a hole into hard, unforgiving soil, plopping in the bulb and then covering with rich, amended soil. Bulb roots go down – they need at least two inches of good soil beneath them.
Light: Allium thrive in full sun, but can tolerate part-shade conditions.
Soil: A well-drained soil is the most important condition for allium as bulbs may rot if left in wet soil. The average soil of most garden beds kept moist but not wet is generally fine.
Spacing: Space depending on the effect you wish to create – for single intensive plantings, space approximately 8-12” apart. For accents with larger varieties, space up to 2’ apart. While some species spread vigorously through seeds or bulbils, many varieties do not spread at all.
Planting: Plant bulbs in fall for a spring bloom. Plant dormant allium bulbs in the fall according to your growing zone. Plant them at a depth of 2-3 times their diameter (4-6”) in a well-drained sunny or partly-shaded site.
Allium is remarkably resilient in a dormant state and can wait to be planted, but needs to be in the ground a few weeks before the ground freezes in order to put down roots. If holding for any length of time, keep cool and dry in a dark location.
Growth Habit: Think: garden lollipop. In early spring, 2-3 flat, strappy leaves will emerge from the soil and remain close to the ground. By late spring, a single hollow flower stalk (scape) will emerge, with a papery tip. The spherical cluster of flowers will emerge when the scape is fully erect, though the foliage may already have started to yellow and die back.
Staking: Allium are remarkably strong for their height, but if you live in an area with high winds, it is wise to stake individual flowers.
Watering: Evenly-moist soil is preferred during the growing season. During the dormant season, bulbs can rot if too much moisture is in the soil.
Fertilizing: A small handful of bone meal placed in the soil at planting time is a good idea for root development. After a season in your garden, mulch with compost or well-rotted manure each year for added trace nutrients and improved soil.
Mulching: Allium doesn’t require mulching, but mulching for moisture retention, nutrients and aesthetics is perfectly okay.
Trimming & Pruning: You can remove the flower clusters either when fresh or dry, but it is crucial to leave the foliage intact, allowing it to yellow and die back naturally. Many gardeners leave the flower heads in place through the autumn as they have an almost architectural appearance.
Allium: End of Season Care
If you’ve already tidied up the foliage after die back and cut off the flower scapes, there is no need to do anything more than wait for spring!
Dividing & Transplanting: Allium do not need to be dug and divided.
Pests & Disease: Insect pests are few and far between when it comes to the genus allium. Moles can dig tunnels under the roots, creating air gaps that will dry out and damage the bulb. Mice, voles and gophers will eat allium if there aren’t tulips and crocus to keep them busy.
Additional Concerns: Some species seed prolifically or create tiny bulbils in the flower head that become tiny plants. It is a good idea to check into the specific variety you are buying to make sure that this isn’t an issue.
Gardening with Allium: Design Advice
There are so many design ideas for allium that the gardener is exceedingly spoiled for choice. As a companion plant for smaller spring bedding plants like forget-me-nots (Myosotis sylvatica) or English daisies (Bellis spp.) it adds drama to an otherwise pretty-but-plain planting.
As a repetitive planting element, it can pull together the informal structure of disparate plants in a cottage garden – creating a stronger sense of purpose for the whole.
A favorite combination is seeing large ‘Globemaster’ allium used to echo the shapes of concrete spheres sitting within planting beds in a formal garden. Equally unexpected is the sight of tall allium breaking through a sea of meadow favorites, like yarrow and ox-eye daisy.
The globe-like multi-flowered heads of allium are very popular with insects and can be used beautifully as accents in a pollinator-friendly garden.
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