When to plant winter squash in zone 3b — planting calendar

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Showing USDA Zone 3B

Growing SeasonZone 3b

Last frost ~May 25First frost ~Sep 15Today

Start indoorsTransplant / sowHarvestFrost risk

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Start indoors May 4 · Sow Jun 8 · First harvest Aug 27 · Wrap by Sep 8

Last spring frostMay 25

Start seeds indoorsMay 4

Direct sowJun 8

First harvestAug 27

Last harvestSep 8

First fall frostSep 15

Why these dates work in zone 3b

Zone 3b's last spring frost averages May 25 and first fall frost Sep 15 — about 113 frost-free days. Winter Squash 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 3 weeks ahead gives strong transplants ready the moment the soil warms.

Common questions

How long does winter squash take to grow in zone 3b?

Winter Squash matures in about 80–110 days from sowing. In zone 3b that means sowing around Jun 8 and first picking around Aug 27.

Will winter squash survive frost in zone 3b?

No — winter squash is frost-sensitive. In zone 3b, wait until after the last frost (around May 25) to plant, and harvest before the first fall frost (around Sep 15).

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