When to plant Sunflower in Zone 3b
In Zone 3b, Sunflower: direct sow outdoors around May 20–Jun 10. Expect to harvest around Jul 29–Aug 19.
| Step | When |
|---|---|
| Direct sow outdoors | May 20 – Jun 10 |
| Harvest | Jul 29 – Aug 19 |
Tip: Direct-sow once frost has passed; sow every two weeks for a long succession of blooms.
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 →