When to plant Sunflower in Zone 4b
In Zone 4b, Sunflower: direct sow outdoors around May 10–May 31. Expect to harvest around Jul 19–Aug 9.
| Step | When |
|---|---|
| Direct sow outdoors | May 10 – May 31 |
| Harvest | Jul 19 – Aug 9 |
Tip: Direct-sow once frost has passed; sow every two weeks for a long succession of blooms.
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 →