When to plant Onion in Zone 10b
In Zone 10b, Onion: start seeds indoors around Nov 6–Nov 20; transplant outdoors around Dec 18–Jan 1. Expect to harvest around Mar 28–Apr 11.
| Step | When |
|---|---|
| Start seeds indoors | Nov 6 – Nov 20 |
| Transplant outdoors | Dec 18 – Jan 1 |
| Harvest | Mar 28 – Apr 11 |
Tip: Day-length sensitive — match the variety (long/short day) to your latitude for big bulbs.
Zone 10b averages a last spring frost around Jan 15 and a first fall frost around Dec 31. These are zone averages — look up your ZIP for your exact area.
See the full Zone 10b calendar in the tool →