When to plant Onion in Zone 3a
In Zone 3a, Onion: start seeds indoors around Mar 16–Mar 30; transplant outdoors around Apr 27–May 11. Expect to harvest around Aug 5–Aug 19.
| Step | When |
|---|---|
| Start seeds indoors | Mar 16 – Mar 30 |
| Transplant outdoors | Apr 27 – May 11 |
| Harvest | Aug 5 – Aug 19 |
Tip: Day-length sensitive — match the variety (long/short day) to your latitude for big bulbs.
Zone 3a averages a last spring frost around May 25 and a first fall frost around Sep 8. These are zone averages — look up your ZIP for your exact area.
See the full Zone 3a calendar in the tool →