When to plant Onion in Zone 3b
In Zone 3b, Onion: start seeds indoors around Mar 11–Mar 25; transplant outdoors around Apr 22–May 6. Expect to harvest around Jul 31–Aug 14.
| Step | When |
|---|---|
| Start seeds indoors | Mar 11 – Mar 25 |
| Transplant outdoors | Apr 22 – May 6 |
| Harvest | Jul 31 – Aug 14 |
Tip: Day-length sensitive — match the variety (long/short day) to your latitude for big bulbs.
Zone 3b averages a last spring frost around May 20 and a first fall frost around Sep 12. These are zone averages — look up your ZIP for your exact area.
See the full Zone 3b calendar in the tool →