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. Nasturtium is frost-sensitive, so the 1w after frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost.
Common questions
How long does nasturtium take to grow in zone 5b?
Nasturtium matures in about 50–70 days from sowing. In zone 5b that means sowing around May 5 and first picking around Jun 24.
Will nasturtium survive frost in zone 5b?
No — nasturtium is frost-sensitive. In zone 5b, wait until after the last frost (around Apr 28) to plant, and harvest before the first fall frost (around Oct 22).
For soil, spacing, pests and companion planting, see the full nasturtium growing guide →