When to plant Onion in Zone 9a
In Zone 9a, Onion: start seeds indoors around Dec 20–Jan 3; transplant outdoors around Jan 31–Feb 14. Expect to harvest around May 11–May 25.
| Step | When |
|---|---|
| Start seeds indoors | Dec 20 – Jan 3 |
| Transplant outdoors | Jan 31 – Feb 14 |
| Harvest | May 11 – May 25 |
Tip: Day-length sensitive — match the variety (long/short day) to your latitude for big bulbs.
Zone 9a averages a last spring frost around Feb 28 and a first fall frost around Dec 5. These are zone averages — look up your ZIP for your exact area.
See the full Zone 9a calendar in the tool →