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. Onion tolerates light frost, so you can sow ahead of the last-frost date and keep harvesting into the cooler fall. Starting seeds indoors 10 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does onion take to grow in zone 7b?
Onion matures in about 90–110 days from sowing. In zone 7b that means sowing around Mar 21 and first picking around Jun 19.
Will onion survive frost in zone 7b?
Yes — onion tolerates light frost. In zone 7b you can sow a little before the last frost (around Apr 4) and keep harvesting past the first fall frost (around Nov 12).
For soil, spacing, pests and companion planting, see the full onion growing guide →