When to plant zinnia
Flower, tender
Penn State lists zinnia as a tender annual and says start those seeds 4–6 weeks before the last frost; Wisconsin says the same lead time and to direct-sow only after frost danger has passed. Germinate around 65–70°F. Flowers stop at frost.
The general rule
- Start indoors
- 4–6 weeks before the last spring frost
- Sow outdoors
- at the last spring frost
- Days to maturity
- Varies by variety
What that means in different climates
The same rule applied to the safer frost dates of cities from cold to frost-free.
| City | Last frost · safer | Start indoors | Sow outdoors |
|---|---|---|---|
| San Jose, CA | Jan 23 | Dec 12 – Dec 26 | Jan 23 – Jan 23 |
| Tucson, AZ | Mar 2 | Jan 19 – Feb 2 | Mar 2 – Mar 2 |
| Portland, OR | Mar 21 | Feb 7 – Feb 21 | Mar 21 – Mar 21 |
| Baltimore, MD | Apr 4 | Feb 21 – Mar 7 | Apr 4 – Apr 4 |
| New York, NY | Apr 12 | Mar 1 – Mar 15 | Apr 12 – Apr 12 |
| Nashville, TN | Apr 16 | Mar 5 – Mar 19 | Apr 16 – Apr 16 |
| Louisville, KY | Apr 23 | Mar 12 – Mar 26 | Apr 23 – Apr 23 |
| Omaha, NE | May 6 | Mar 25 – Apr 8 | May 6 – May 6 |
| Colorado Springs, CO | May 15 | Apr 3 – Apr 17 | May 15 – May 15 |
| Miami, FL | Frost rare | Frost is rare: late winter to spring; late summer to fall. | |