WhenToPlantGuide

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When to plant onions

Plant onions 2–4 weeks before the last spring frost. Wait until the soil is at least 45°F. That works out to zone 5b (early April to late April), zone 7a (mid March to early April) and zone 9a (early February to mid February).

Onions planting dates by zone

JanFebMarAprMayJunJulAugSepOctNovDec 2a Start indoors Mar 11 – Mar 25 Plant Apr 22 – May 6 3b Start indoors Mar 8 – Mar 22 Plant Apr 19 – May 3 4a Start indoors Mar 6 – Mar 20 Plant Apr 17 – May 1 4b Start indoors Mar 4 – Mar 18 Plant Apr 15 – Apr 29 5a Start indoors Mar 2 – Mar 16 Plant Apr 13 – Apr 27 5b Start indoors Feb 24 – Mar 10 Plant Apr 7 – Apr 21 6a Start indoors Feb 19 – Mar 5 Plant Apr 2 – Apr 16 6b Start indoors Feb 13 – Feb 27 Plant Mar 27 – Apr 10 7a Start indoors Feb 4 – Feb 18 Plant Mar 18 – Apr 1 7b Start indoors Jan 26 – Feb 9 Plant Mar 9 – Mar 23 8a Start indoors Jan 16 – Jan 30 Plant Feb 27 – Mar 13 8b Start indoors Jan 5 – Jan 19 Plant Feb 16 – Mar 2 9a Start indoors Dec 22 – Jan 5 Plant Feb 2 – Feb 16 9b Start indoors Nov 26 – Dec 10 Plant Jan 7 – Jan 21 10a Start indoors Oct 30 – Nov 13 Plant Dec 11 – Dec 25
■ spring planting · ■ start seeds indoors. Zones from the USDA 2023 map; dates from NOAA frost normals for the weather stations in each zone.
ZonePlant outdoorsonions ready from
4a Apr 17 – May 1 Jul 23
4b Apr 15 – Apr 29 Jul 21
5a Apr 13 – Apr 27 Jul 19
5b Apr 7 – Apr 21 Jul 13
6a Apr 2 – Apr 16 Jul 8
6b Mar 27 – Apr 10 Jul 2
7a Mar 18 – Apr 1 Jun 23
7b Mar 9 – Mar 23 Jun 14
8a Feb 27 – Mar 13 Jun 4
8b Feb 16 – Mar 2 May 24
9a Feb 2 – Feb 16 May 10
9b Jan 7 – Jan 21 Apr 14

How to plant onions

Plant assets or transplants
Soil temperature45°F or warmer
Depth1 in (sets), 1/2 in (seed)
Spacing4–6 in
LightFull sun
Time to harvest90–120 days
Start indoors8–10 weeks before the last frost (zone 6a: Feb 19 – Mar 5; zone 8a: Jan 16 – Jan 30)

Choose the day-length type for your latitude: long-day onions in the North, short-day in the South.

Onions handle frost, so they are one of the first things planted.

Bulb size depends on how many leaves grow before bulbing starts, so early planting gives bigger onions.

When to harvest onions

When most tops fall over, pull the bulbs and cure them in a dry, airy place for 2–3 weeks before storing.

Planting onions in warm climates

In the South (zones 8–10) short-day onions are planted in fall or winter, roughly October–January.

Exact dates for your town: planting calendar · frost dates by state.

More vegetables to plant

Tomatoes · Bell peppers · Potatoes · Pumpkins · Cucumbers · Okra · Zucchini · Watermelon