When to plant onion in zone 9a — planting calendar

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Showing USDA Zone 9A

Growing SeasonZone 9a

Last frost ~Feb 28First frost ~Nov 30Today

Start indoorsTransplant / sowHarvestFrost risk

DECJANFEBMARAPRMAYJUN

Start indoors Dec 20 · Sow Feb 14 · First harvest May 15 · Wrap by Jun 12

Last spring frostFeb 28

Start seeds indoorsDec 20

Direct sowFeb 14

First harvestMay 15

Last harvestJun 12

First fall frostNov 30

Why these dates work in zone 9a

Zone 9a's last spring frost averages Feb 28 and first fall frost Nov 30 — about 275 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 9a?

Onion matures in about 90–110 days from sowing. In zone 9a that means sowing around Feb 14 and first picking around May 15.

Will onion survive frost in zone 9a?

Yes — onion tolerates light frost. In zone 9a you can sow a little before the last frost (around Feb 28) and keep harvesting past the first fall frost (around Nov 30).

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