Also known as Ornamental Onion · 2.3k saves
Allium
Allium, the genus most gardeners know as ornamental onion. We track 56 varieties; the ones most used by real gardeners.
The 24 most-saved Allium varieties
See all 56 Allium varieties →Search this genus →
24 species of Allium
Each one is a parent of the varieties above.
Track your Allium in Sow
Save the Allium you grow and get care reminders timed to your zone.
How to grow Allium
Whats common across all Allium varieties in our catalog — drawn from the care records of the 40 most-grown of them.
The Allium year
- PlantSeptember–November90% of varieties
Plant bulbs 4-6 inches deep in well-drained soil during fall
- FertilizeFebruary and March80% of varieties
Apply a balanced bulb fertilizer as new shoots emerge in spring
- DivideAugust and September55% of varieties
Divide crowded clumps every 3-4 years after foliage dies back
- DeadheadMay and June43% of varieties
Remove spent flower heads, but leave foliage until it yellows naturally
- HarvestMay–August43% of varieties
Harvest when tops yellow and fall over; cure bulbs in a dry, shaded spot
- Spring CleanupFebruary and March33% of varieties
Remove old, dead foliage before new shoots emerge
Do
- Water regularly during active growth 🌱
- Mulch to retain moisture and suppress weeds
- Apply balanced fertilizer in early spring
- Water during dry spells 🌱
- Water consistently during dry spells 💧
Avoid
- Avoid overwatering to prevent bulb rot ❌
- Avoid overwatering in winter ❌
- Overwater to prevent bulb rot ❌
- Do not plant in heavy clay soil without amendment
What goes wrong with Allium
| Problem | What you'll see | What to do |
|---|---|---|
| Aphids | Sticky residue and distorted leaves | Spray with neem oil or insecticidal soap |
| Onion Maggot | Wilting and rotting bulbs | Use beneficial nematodes or apply insecticidal soap |
| Onion maggot | Wilting and rotting bulbs | Apply beneficial nematodes or crop rotation |
| Onion Maggots | Stunted growth and rotting bulbs | Use crop rotation and organic beneficial nematodes |
| Downy Mildew | Grayish-purple fuzzy growth on leaves, followed by yellowing. | Improve air circulation. Avoid overhead watering. Fungicides are rarely necessary. |
| Gray Mold | Gray fuzzy mold on leaves and bulbs | Improve air circulation and apply fungicide |
| Downy mildew | Grey mold on leaves | Ensure good air circulation and avoid overhead watering |
Making more Allium
Division
- Divide mature clumps in early fall (6 weeks).
- Replant divisions immediately in well-drained soil.
Bulb division
- Lift bulbs in late summer
- Separate offsets with clean tools
- Replant immediately in well-prepared soil
Allium questions
How many types of Allium are there?
The Sow catalog tracks 56 distinct Allium varieties. The most popular — ranked by 2.3k real gardeners — are shown first above.
What zones does Allium grow in?
Across its varieties, Allium covers USDA Zones 4–10. Individual varieties differ — each plant page lists its exact range, and Sow filters the catalog to your zone automatically.
When does Allium bloom?
Most Allium varieties bloom in mid-summer, late spring to early summer, late spring. Staggering early, mid, and late varieties extends the genus's season in one bed.
Which Allium should I choose?
Start from the most-saved varieties above — popularity across thousands of gardens is a strong signal of reliability — then filter by your zone and sun. In the Sow app you can preview any of them in a photo of your actual yard before you buy.