When to plant Cosmos in Zone 1b
In Zone 1b, Cosmos: direct sow outdoors around Jun 10–Jun 24. Expect to harvest around Aug 9–Aug 23.
| Step | When |
|---|---|
| Direct sow outdoors | Jun 10 – Jun 24 |
| Harvest | Aug 9 – Aug 23 |
Tip: Thrives on neglect — too-rich soil gives leaves at the expense of flowers.
Zone 1b averages a last spring frost around Jun 10 and a first fall frost around Aug 20. These are zone averages — look up your ZIP for your exact area.
See the full Zone 1b calendar in the tool →