Ornamental Allium in Zone 5a & 5b
Allium spp. (flowering onion)
Yes, ornamental allium grows in zones 5a and 5b. Plant it outside in Sep–Nov. For a fall crop, plant out in Sep–Nov.
When to plant ornamental allium in zone 5b
Zones 5a and 5b share the same average frost dates, so this page covers both.
Method: Direct sow: Direct-sow outside. It doesn't transplant well, or doesn't need the extra time indoors.
| Window | Fall window |
|---|---|
| Start indoors | Not typically started indoors |
| Direct sow / transplant outside | Sep–Nov |
| Estimated bloom | ~195 days after direct-sowing |
Spacing: 5 per square foot (square-foot-gardening spacing). Mature height: 2-3 ft.
Zone 5b dates sourced from www.longfield-gardens.com.
Fall window: the last sowing date is the average first frost minus days to maturity, the method in Purdue Extension's fall garden guide, which lists ornamental allium for late-summer planting.
Plant alongside it in zone 5b
These go outside within two weeks of ornamental allium in zone 5b, so one planting day can cover them.
- CrocusSep–Nov
- Daffodil (Narcissus)Sep–Nov
- Dutch IrisSep–Nov
- HyacinthSep–Nov
Ornamental allium is the flowering relative of the onion you eat, grown for its round, spiky flower heads on tall bare stems rather than for anything edible. It blooms in the awkward late-spring gap after tulips finish and before most perennials are in full swing, which is exactly why gardeners plant it.
How ornamental allium fits zone 5's season
Zone 5b's frost-free window runs about 148 days, from May 10 to October 5. Ornamental allium goes in during the fall and grows through the winter, so it isn't limited by this window: expect first bloom about 195 days after planting.
Ornamental Allium planting windows in every zone
Zone 5b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 3a & 3bFall window | Not usually | Sep–Nov | ~195 days after direct-sowing |
| 4a & 4bFall window | Not usually | Sep–Nov | ~195 days after direct-sowing |
| 5a & 5bFall window (your zone) | Not usually | Sep–Nov | ~195 days after direct-sowing |
| 6a & 6bFall window | Not usually | Sep–Nov | ~195 days after direct-sowing |
| 7a & 7bFall window | Not usually | Sep–Nov | ~195 days after direct-sowing |
| 8a & 8bFall window | Not usually | Sep–Nov | ~195 days after direct-sowing |
Bloom dates are about 195 days after the sow or plant-out date.
Good companions
No well-established companions for ornamental allium.
Where to buy ornamental allium bulbs
We haven't vetted bulb/tuber suppliers yet. Our seed-supplier list below doesn't carry these. The growing-guide source cited above is a good starting point for where to buy.
As an Amazon Associate we earn from qualifying purchases. Some links on this page also go to other retailers we may earn a commission from as an affiliate, at no extra cost to you. We only recommend products with a clear consensus of positive, independent reviews, or ones we bought and use ourselves. Each item on our gear page says which.
See it growing
Search YouTube for "growing ornamental allium" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 5b calendar · Plan your beds in the Garden Designer →
Pin this for later
Growing Ornamental Allium in USDA zone 5b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
Save to Pinterest