When to plant onion in zone 8b — planting calendar

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Showing USDA Zone 8B

Growing SeasonZone 8b

Last frost ~Mar 15First frost ~Nov 15Today

Start indoorsTransplant / sowHarvestFrost risk

DECJANFEBMARAPRMAYJUNJUL

Start indoors Jan 4 · Sow Mar 1 · First harvest May 30 · Wrap by Jun 27

Last spring frostMar 15

Start seeds indoorsJan 4

Direct sowMar 1

First harvestMay 30

Last harvestJun 27

First fall frostNov 15

Why these dates work in zone 8b

Zone 8b's last spring frost averages Mar 15 and first fall frost Nov 15 — about 245 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 8b?

Onion matures in about 90–110 days from sowing. In zone 8b that means sowing around Mar 1 and first picking around May 30.

Will onion survive frost in zone 8b?

Yes — onion tolerates light frost. In zone 8b you can sow a little before the last frost (around Mar 15) and keep harvesting past the first fall frost (around Nov 15).

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