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Allium Planting Guide

If you don't already consider onions to be gorgeous garden additions, we're about to change your mind with these ornamental balls of joy! As with garlic and onions, Alliums display round flower heads, and while they may not spice up your cooking, they do exhibit a subtle onion-like aroma when crushed. Each spherical cluster comprises dozens of striking, star-shaped florets that are sure to brighten your garden. They are remarkably tough plants—excellent for cutting, attractive to pollinators, and resistant to drought, cold, and rodents. Blooming from late spring to early summer, these fluffy globes range in height from 12" up to 4' with some blossoms being as large as soccer balls. Take your garden to the next level of dramatic design with gorgeous Alliums!

Success Snapshot

PLANTING
DEPTH

Species dependent; 4-8"

WATER
QUANTITY

Moderate to Low

SUNLIGHT
QUANTITY

Full Sun

PLANTING
PROXIMITY

6-8" Apart

BLOOM
SEASON

Late Spring - Summer

HARDINESS
ZONES

Species Dependent

Where to Plant

Alliums thrive in locations with rich, well-drained soil and full sun but will tolerate partial shade. If you notice water puddles 5–6 hours after a hard rain, you'll want to find another site or amend the soil with the addition of organic material to improve drainage. Alliums aren't fussy about soil, but they will not survive in soggy conditions or standing water. If using containers, make sure there are adequate drainage holes and keep in mind the mature size of the varieties you have chosen to plan your container sizes accordingly.


When to Plant

Allium bulbs are typically planted when dormant in the fall. While they are remarkably resilient in a dormant state and will tolerate waiting, they should be planted a few weeks before the ground freezes. After planting, their roots will form, and you can expect blooms to arrive in late spring or early summer.


How to Plant

  • Find a location where your Alliums will receive full sun, as they develop stronger stems in brighter light.
  • Fill containers, if you're using them, with good quality, well-drained soil. Almost any commercially available potting medium will do the trick.
  • Dig holes and bury the bulbs 4–8" deep and 6"–8" apart with the pointy end facing up.
  • Water thoroughly after planting to settle the soil around the bulbs.

How to Grow

  • Water as needed during active growth, aiming for about 1" of moisture per week.
  • Stake taller Alliums to avoid breakage. Shorter varieties don’t require staking.
  • Leave the foliage in place after blooms have faded. The leaves will gather sunlight to create food through photosynthesis, strengthening the bulb for the future.
  • Remove the foliage in mid-summer when the leaves turn yellow and die back as the plant slips into dormancy. This clean-up will give your Allium a clean slate before beginning the next growing cycle.

Allium Tips & Tricks

  • Snip a few of these brilliant blooms during the growth period for striking arrangements or for drying. Don’t worry—this won’t hurt your plants!
  • Expect the most substantial top growth and flower stems to arrive in the spring. Those in warmer climates may also develop a few sprouts in autumn.
  • Amend soil with compost, ground bark, or decomposed manure as needed to avoid water-logging your plant.
  • Plant a clump of Allium bulbs for magnificent clusters of blooms rather than a stand-alone display.