Last spring frostMay 7
Start seeds indoorsMar 26
Direct sowMay 7
First harvestJun 21
Last harvestOct 6
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. Marigold is frost-sensitive, so the around last frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost. Starting seeds indoors 6 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does marigold take to grow in zone 4a?
Marigold matures in about 45–55 days from sowing. In zone 4a that means sowing around May 7 and first picking around Jun 21.
Will marigold survive frost in zone 4a?
No — marigold 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 marigold growing guide →