When to plant Onion in Zone 9b
In Zone 9b, Onion: start seeds indoors around Dec 7–Dec 21; transplant outdoors around Jan 18–Feb 1. Expect to harvest around Apr 28–May 12.
| Step | When |
|---|---|
| Start seeds indoors | Dec 7 – Dec 21 |
| Transplant outdoors | Jan 18 – Feb 1 |
| Harvest | Apr 28 – May 12 |
Tip: Day-length sensitive — match the variety (long/short day) to your latitude for big bulbs.
Zone 9b averages a last spring frost around Feb 15 and a first fall frost around Dec 15. These are zone averages — look up your ZIP for your exact area.
See the full Zone 9b calendar in the tool →