Zone 8b covers 47 days of last-frost dates. We measured Fort Worth, TX at Feb 18 and Eugene, OR at Apr 6. 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 8b
Zone 8b's last spring frost averages Mar 6 and first fall frost Nov 22 — about 261 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 8b?
Onion matures in about 90–110 days from sowing. In zone 8b that means sowing around Feb 20 and first picking around May 21.
Will onion survive frost in zone 8b?
Yes — onion tolerates light frost. In zone 8b you can sow a little before the last frost (around Mar 6) and keep harvesting past the first fall frost (around Nov 22).
For soil, spacing, pests and companion planting, see the full onion growing guide →