Zone 5b covers 25 days of last-frost dates. We measured Davenport, IA at Apr 16 and Idaho Falls, ID at May 11. 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 5b
Zone 5b's last spring frost averages Apr 28 and first fall frost Oct 22 — about 177 frost-free days. Broccoli tolerates light frost, so you can set plants out ahead of the last-frost date and keep harvesting into the cooler fall. Starting seeds indoors 6 weeks ahead gives strong transplants ready the moment the soil warms. There's also room for a fall succession sowing around Jul 23 for a second harvest before frost.
Common questions
How long does broccoli take to grow in zone 5b?
Broccoli matures in about 80–100 days from transplanting. In zone 5b that means setting plants out around Apr 7 and first picking around Jun 26.
Will broccoli survive frost in zone 5b?
Yes — broccoli tolerates light frost. In zone 5b you can set plants out a little before the last frost (around Apr 28) and keep harvesting past the first fall frost (around Oct 22).
Can I plant a second crop of broccoli in zone 5b?
Yes — in zone 5b there's time for a fall sowing around Jul 23 for a second harvest before frost.
For soil, spacing, pests and companion planting, see the full broccoli growing guide →