Zone 5a covers 27 days of last-frost dates. We measured Sioux City, IA at Apr 20 and Bozeman, MT at May 17. 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 5a
Zone 5a's last spring frost averages Apr 30 and first fall frost Oct 20 — about 173 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 21 for a second harvest before frost.
Common questions
How long does broccoli take to grow in zone 5a?
Broccoli matures in about 80–100 days from transplanting. In zone 5a that means setting plants out around Apr 9 and first picking around Jun 28.
Will broccoli survive frost in zone 5a?
Yes — broccoli tolerates light frost. In zone 5a you can set plants out a little before the last frost (around Apr 30) and keep harvesting past the first fall frost (around Oct 20).
Can I plant a second crop of broccoli in zone 5a?
Yes — in zone 5a there's time for a fall sowing around Jul 21 for a second harvest before frost.
For soil, spacing, pests and companion planting, see the full broccoli growing guide →