When to plant basil in zone 4a — planting calendar

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Showing USDA Zone 4A

Growing SeasonZone 4a

Last frost ~May 20First frost ~Sep 20Today

Start indoorsTransplant / sowHarvestFrost risk

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Start indoors Apr 22 · Sow Jun 3 · First harvest Jun 28 · Wrap by Sep 13

Last spring frostMay 20

Start seeds indoorsApr 22

Direct sowJun 3

First harvestJun 28

Last harvestSep 13

First fall frostSep 20

Why these dates work in zone 4a

Zone 4a's last spring frost averages May 20 and first fall frost Sep 20 — about 123 frost-free days. Basil is frost-sensitive, so the 2w after 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 4 weeks ahead gives strong transplants ready the moment the soil warms.

Common questions

How long does basil take to grow in zone 4a?

Basil matures in about 25–35 days from sowing. In zone 4a that means sowing around Jun 3 and first picking around Jun 28.

Will basil survive frost in zone 4a?

No — basil is frost-sensitive. In zone 4a, wait until after the last frost (around May 20) to plant, and harvest before the first fall frost (around Sep 20).

For soil, spacing, pests and companion planting, see the full basil growing guide →