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Allium Planting Guide

Alliums are in the same family as garlic, onions, chives and shallots. Given that lineage ornamental gardeners sometimes wonder if including alliums will cause their borders to smell like salad bars. Not to worry. The scent, when present at all, is mild and noticeable only when the leaves are bruised or crushed. Onion family members are unappealing to rodents, however, and that's a real plus in many regions where critters are an ongoing challenge. What flowering onions introduce into your landscape is drama. The blooms of these plants are mostly globes on slim, straight stems, often of incredible size. Some blossoms are as large as soccer balls and perch atop 3½ foot stalks. Few plants can provide that kind of "Wow!" and if you garden with children, be sure to include alliums. Kids love these!

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

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Outdoor Beds

  1. Find a location where the soil drains well. If there are still water puddles 5-6 hours after a hard rain, scout out another site. Or amend the soil with the addition of organic material to raise the level 2-3" to improve the drainage. Peat moss, compost, ground bark or decomposed manure all work well and are widely available. While alliums aren't fussy about soil, they will not survive in soggy soil or standing water.
  2. Site your alliums where they will receive full sun. Alliums will grow in light shade but tend to develop stronger stems in brighter light.
  3. Dig holes and plant the bulbs 4-8" deep and 6"-8" apart, depending on the variety. Position the bulbs with the pointy end facing up.
  4. After planting, water well to settle the soil around the bulbs. Roots will form in the fall. A few sprouts may also develop in autumn if you live in a warm region. More substantial top growth and flower stems will form in the spring.
  5. When in bloom, feel free to cut allium flowers for striking bouquets or for drying.
  6. After blooming has finished for the season leave the foliage in place; don't cut it off. The leaves will gather sunlight, create food through photosynthesis and strengthen the bulb for the future. Water as needed during active growth periods, about 1" of moisture per week is a good estimate.
  7. By mid summer the leaves will yellow and die back as the plant slips into dormancy. Foliage many be removed at this point. Your alliums will rest for a few months before beginning the next growing cycle.

Pots, Barrels, Tubs & Urns

  1. Fill your containers with good quality, well-drained soil. Almost any commercially available potting medium will work fine. Make sure there are adequate drainage holes; allium bulbs must never sit in waterlogged soil or they will rot. Keep in mind the mature size of the varieties you have chosen and plan your container sizes accordingly.
  2. Site your containers where they will receive full sun.
  3. Plant your alliums 4-8" deep and 6"-8" apart, depending on the variety, for the most brilliant display. Position bulbs with the pointy ends up.
  4. After planting, water your containers well, gently soaking the soil so it settles around the bulbs. Roots will form in the fall. A few sprouts may also develop in autumn if you live in a warm region. Taller top growth and flower stems will form in the spring.
  5. Enjoy your flowering containers, snipping a few flowers if you like. This won't hurt your plants.
  6. After blooming has finished for the season leave the foliage in place; don't cut it off. The leaves will gather sunlight, create food through photosynthesis and strengthen the bulb for the future. Water as needed during active growth periods, about 1" per week.
  7. By mid summer the leaves will yellow and die back as the plant slips into dormancy. Foliage many be removed at this point. Your alliums will rest for a few months before beginning the next growing cycle.