When to plant onion in zone 6b — planting calendar

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Showing USDA Zone 6B

Growing SeasonZone 6b

Last frost ~Apr 20First frost ~Oct 15Today

Start indoorsTransplant / sowHarvestFrost risk

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Start indoors Feb 9 · Sow Apr 6 · First harvest Jul 5 · Wrap by Aug 2

Last spring frostApr 20

Start seeds indoorsFeb 9

Direct sowApr 6

First harvestJul 5

Last harvestAug 2

First fall frostOct 15

Why these dates work in zone 6b

Zone 6b's last spring frost averages Apr 20 and first fall frost Oct 15 — about 178 frost-free days. Onion tolerates light frost, so you can sow ahead of the last-frost date and keep harvesting into the cooler fall. Starting seeds indoors 10 weeks ahead gives strong transplants ready the moment the soil warms.

Common questions

How long does onion take to grow in zone 6b?

Onion matures in about 90–110 days from sowing. In zone 6b that means sowing around Apr 6 and first picking around Jul 5.

Will onion survive frost in zone 6b?

Yes — onion tolerates light frost. In zone 6b you can sow a little before the last frost (around Apr 20) and keep harvesting past the first fall frost (around Oct 15).

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