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. Bok Choy 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 4 weeks ahead gives strong transplants ready the moment the soil warms. There's also room for a fall succession sowing around Aug 27 for a second harvest before frost.
Common questions
How long does bok choy take to grow in zone 5b?
Bok Choy matures in about 45–60 days from transplanting. In zone 5b that means setting plants out around Apr 7 and first picking around May 22.
Will bok choy survive frost in zone 5b?
Yes — bok choy 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 bok choy in zone 5b?
Yes — in zone 5b there's time for a fall sowing around Aug 27 for a second harvest before frost.
For soil, spacing, pests and companion planting, see the full bok choy growing guide →