When to plant Rosemary in Zone 4b
In Zone 4b, Rosemary: start seeds indoors around Mar 1–Mar 15; transplant outdoors around May 24–Jun 7. Expect to harvest around Aug 22–Sep 5.
| Step | When |
|---|---|
| Start seeds indoors | Mar 1 – Mar 15 |
| Transplant outdoors | May 24 – Jun 7 |
| Harvest | Aug 22 – Sep 5 |
Tip: Slow from seed and frost-tender in cold zones — most gardeners start from a plant and overwinter indoors.
Zone 4b averages a last spring frost around May 10 and a first fall frost around Sep 22. These are zone averages — look up your ZIP for your exact area.
See the full Zone 4b calendar in the tool →