Plant Onions in Zone 12b
Seed-starting, transplant & harvest dates for USDA Zone 12b
Zone 12b is effectively frost-free, so the Zone 12b calendar for onions is set by heat, not cold. There is no last frost to count backward from and no first frost to beat, which means the question is not whether onions will finish but whether it will sit through the hottest stretch of the year. Onions is a hardy crop needing about 100 days from sowing to harvest.
Planting onions for a fall harvest in Zone 12b
Zone 12b has no meaningful frost, so the fall and winter months are the easiest time of year to grow onions here. Sow from about October 1 onward.
Short-day onion sets planted in fall overwinter in zone 7 and warmer and bulb up months ahead of a spring planting.
Fall dates are counted backward from the Zone 12b average first frost, not forward from a sowing date. See the fall planting calendar by zone for the full method.
Spring vs fall onions in Zone 12b
| Planting | Sow or start | In the ground | Harvest |
|---|---|---|---|
| Spring | Feb 1 | Feb 1 | May 12 |
| Fall | Oct onward | Oct onward | Next spring |
Onions in nearby zones
Further reading on onions
- When to plant garlic by zone
The fall planting window for garlic and other alliums in every zone.
- When to start seeds indoors by zone
Indoor start dates for onions, counted back from your last frost.
- Hardening off seedlings: a schedule
A day by day plan for moving onions seedlings outdoors.
Other crops in Zone 12b
Frequently asked questions
When should I start onions in Zone 12b?
Direct sow outdoors around Feb 1.
Can I direct sow onions in Zone 12b?
Yes, direct sow around Feb 1.
Can I plant onions in the fall in Zone 12b?
Zone 12b has no meaningful frost, so the fall and winter months are the easiest time of year to grow onions here. Sow from about October 1 onward.
Will onions survive frost in Zone 12b?
Onions is a hardy crop and keeps going roughly 21 days past the first light frost in Zone 12b. A row cover or a straw mulch buys more.