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. Lemon Balm 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.
Common questions
How long does lemon balm take to grow in zone 5b?
Lemon Balm matures in about 60–90 days from transplanting. In zone 5b that means setting plants out around Apr 28 and first picking around Jun 27.
Will lemon balm survive frost in zone 5b?
Yes — lemon balm 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).
For soil, spacing, pests and companion planting, see the full lemon balm growing guide →