When to plant Cosmos in Zone 5a
In Zone 5a, Cosmos: direct sow outdoors around May 5–May 19. Expect to harvest around Jul 4–Jul 18.
| Step | When |
|---|---|
| Direct sow outdoors | May 5 – May 19 |
| Harvest | Jul 4 – Jul 18 |
Tip: Thrives on neglect — too-rich soil gives leaves at the expense of flowers.
Zone 5a averages a last spring frost around May 5 and a first fall frost around Oct 1. These are zone averages — look up your ZIP for your exact area.
See the full Zone 5a calendar in the tool →