DibbleWhen to plant Cosmos
Sow cosmos after last frost in lean soil, too much fertility means leaves, not flowers. Deadhead for continuous bloom.
When to plant Cosmos by zone
| Zone | Start seeds indoors | Sow or transplant | Harvest |
|---|---|---|---|
| Zone 3 | not needed | May 22 | July 31 |
| Zone 4 | not needed | May 17 | July 26 |
| Zone 5 | not needed | May 7 | July 16 |
| Zone 6 | not needed | April 28 | July 7 |
| Zone 7 | not needed | April 17 | June 26 |
| Zone 8 | not needed | April 4 | June 13 |
| Zone 9 | not needed | March 8 | May 17 |
| Zone 10 | not needed | February 7 | April 18 |
| Zone 11 | not needed | January 8 | March 19 |
These dates use typical frost dates for each zone. Dibble tunes them to your exact ZIP and lets you adjust frost dates for your own yard.
Companion plants
Good neighbors for Cosmos:
Family and rotation
Cosmos is in the asters family. Lettuce and many flowers. Marigolds and zinnias are excellent companions throughout the garden. Learn about crop rotation.
Related crops
Lettuce
When to plantDahlia
When to plantZinnia
When to plantSunflower
When to plantMarigold
When to plantCalendula
When to plantQuestions
When should I plant cosmos?
It depends on your zone. Cosmos is a tender crop, so the timing follows your last spring frost. Look up your zone in the table below for exact start, sow, and harvest dates, or open Dibble and enter your ZIP to get your own calendar.
How long does cosmos take to grow?
About 70 days from sowing to the first harvest, with a picking window of roughly 70 days after that.
What grows well with cosmos?
Good companions include Zinnia, Sunflower.
Plant at the right time this season
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