When to plant Cosmos in Zone 1a
In Zone 1a, Cosmos: direct sow outdoors around Jun 15–Jun 29. Expect to harvest around Aug 14–Aug 28.
| Step | When |
|---|---|
| Direct sow outdoors | Jun 15 – Jun 29 |
| Harvest | Aug 14 – Aug 28 |
Tip: Thrives on neglect — too-rich soil gives leaves at the expense of flowers.
Zone 1a averages a last spring frost around Jun 15 and a first fall frost around Aug 15. These are zone averages — look up your ZIP for your exact area.
See the full Zone 1a calendar in the tool →