When to plant Sunflower in Zone 4a
In Zone 4a, Sunflower: direct sow outdoors around May 15–Jun 5. Expect to harvest around Jul 24–Aug 14.
| Step | When |
|---|---|
| Direct sow outdoors | May 15 – Jun 5 |
| Harvest | Jul 24 – Aug 14 |
Tip: Direct-sow once frost has passed; sow every two weeks for a long succession of blooms.
Zone 4a averages a last spring frost around May 15 and a first fall frost around Sep 18. These are zone averages — look up your ZIP for your exact area.
See the full Zone 4a calendar in the tool →