Zone 7b covers 44 days of last-frost dates. We measured Oklahoma City, OK at Mar 12 and Reno, NV at Apr 25. Give us your town or ZIP and we'll use ten years of daily lows recorded at your own coordinates instead of the middle of that range.
Why these dates work in zone 7b
Zone 7b's last spring frost averages Apr 4 and first fall frost Nov 12 — about 222 frost-free days. Zinnia is frost-sensitive, so the around last frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost. Starting seeds indoors 4 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does zinnia take to grow in zone 7b?
Zinnia matures in about 50–70 days from sowing. In zone 7b that means sowing around Apr 4 and first picking around May 24.
Will zinnia survive frost in zone 7b?
No — zinnia is frost-sensitive. In zone 7b, wait until after the last frost (around Apr 4) to plant, and harvest before the first fall frost (around Nov 12).
For soil, spacing, pests and companion planting, see the full zinnia growing guide →