Last spring frostMay 7
Direct sowMay 14
First harvestJul 3
Last harvestSep 25
First fall frostOct 13
Why these dates work in zone 4a
Zone 4a's last spring frost averages May 7 and first fall frost Oct 13 — about 159 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 4a?
Nasturtium matures in about 50–70 days from sowing. In zone 4a that means sowing around May 14 and first picking around Jul 3.
Will nasturtium survive frost in zone 4a?
No — nasturtium is frost-sensitive. In zone 4a, wait until after the last frost (around May 7) to plant, and harvest before the first fall frost (around Oct 13).
For soil, spacing, pests and companion planting, see the full nasturtium growing guide →