When to Plant Zinnias
Zinnias are a tender warm-season flower. Frost damages them, so they go out only after the last spring frost.
Start seeds indoors 2 to 4 weeks before the last spring frost, and plant out 1 to 3 weeks after the last frost. Or sow them where they will grow, 1 to 3 weeks after the last spring frost. The first flowers open about 56 to 84 days after sowing.
Example dates
The same rules in dates for three climates, using typical frost dates. Enter your ZIP code above for the dates where you live.
| Task | Last frost Mar 15first Nov 15 | Last frost Apr 15first Oct 25 | Last frost May 15first Sep 30 |
|---|---|---|---|
| Start seeds indoors | Feb 15 – Mar 1 | Mar 18 – Apr 1 | Apr 17 – May 1 |
| Harden off | Mar 15 – 21 | Apr 15 – 21 | May 15 – 21 |
| Plant out | Mar 22 – Apr 5 | Apr 22 – May 6 | May 22 – Jun 5 |
| In flower | Apr 12 – Jul 5 | May 13 – Aug 5 | Jun 12 – Sep 4 |
| Direct-sown: Sow outdoors | Mar 22 – Apr 5 | Apr 22 – May 6 | May 22 – Jun 5 |
| Direct-sown: In flower | May 17 – Aug 9 | Jun 17 – Sep 9 | Jul 17 – Oct 9 |
Growing zinnias
Sow into warm soil after frost and cut flowers often to encourage more stems.
- Spacing: 12 in apart, in rows 18 in apart. In a raised bed, 1 per sq ft at square-foot spacing.
- Days to first flowers: 56 to 84 from sowing, then about 12 weeks of flowers.
- Traditional companions: kale. See companion plants for zinnias.
Plan your beds with these dates
Draw your beds, tap squares to plant zinnias and everything else, and get every crop's dates for your ZIP code in one calendar. Free, in your browser.
Open the garden plannerQuestions
When do I start zinnias indoors?
2 to 4 weeks before the last spring frost: with a last frost of April 15, that's Mar 18 – Apr 1. Enter your ZIP code above for your own dates.
Can zinnias go in before the last frost?
No. Zinnias are damaged by frost: plant them out 1 to 3 weeks after the last spring frost.
How long do zinnias take to grow?
About 56 to 84 days from sowing to the first flowers, which then lasts about 12 weeks. Varieties differ: check the seed packet.
More planting dates
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020 (annual/seasonal, by station: freeze dates at 32 °F)
- NC State Extension: Extension Gardener Handbook, Chapter 16: Vegetable Gardening
- Iowa State: Germination Requirements for Annuals and Vegetables
- Purdue University Extension: Starting Seeds Indoors (HO-14-W)
- Colorado State University Extension: Growing Annual Plants from Seed
- Colorado State University Extension: How to grow, harvest and eat 12 tasty edible annual flowers in Colorado
- Clemson Cooperative Extension HGIC: How to Grow Zinnias: The Best Varieties & Care Tips