Plant Onions in Zone 8a

Seed-starting, transplant & harvest dates for USDA Zone 8a

Start indoors

Jan 14

Transplant

Mar 11

Harvest (~100d)

Jun 19

Zone 8a averages 228 frost-free days, running from a last spring frost around March 25 to a first fall frost around November 8. Onions needs roughly 100 days from planting out to first harvest, so it uses about 44 percent of that window. Onions is a hardy crop, which is what decides where in the window it belongs.

Because onions needs a head start, sow seed indoors around Jan 14, about 10 weeks ahead of the Zone 8a last frost. Transplants go out around Mar 11. Starting earlier than that in Zone 8a usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 100 days to harvest, a 228-day Zone 8a season has room for about 2 sowings, so stagger them rather than planting everything at once.

Planting onions for a fall harvest in Zone 8a

Yes. Plant onions between September 27 and October 18 in Zone 8a, roughly 6 to 3 weeks before the average first frost, so it roots before the ground freezes.

Short-day onion sets planted in fall overwinter in zone 7 and warmer and bulb up months ahead of a spring planting.

Plant from

Sep 27

Plant by

Oct 18

Overwinters, harvest in spring

Spring

Fall dates are counted backward from the Zone 8a average first frost, not forward from a sowing date. See the fall planting calendar by zone for the full method.

Spring vs fall onions in Zone 8a

Planting	Sow or start	In the ground	Harvest
Spring	Jan 14	Mar 11	Jun 19
Fall	by Oct 18	Oct 18	Next spring

Last spring frost

Mar 25

First fall frost

Nov 8

Growing season

228 days

Onions in nearby zones

Onions in Zone 7b (colder) Onions in Zone 8b (warmer) Full Onions grow guide Zone 8a planting calendar

Other crops in Zone 8a

Tomatoes in Zone 8a Peppers in Zone 8a Cucumbers in Zone 8a Lettuce in Zone 8a Zucchini in Zone 8a Carrots in Zone 8a Beans (bush) in Zone 8a Peas in Zone 8a Broccoli in Zone 8a Spinach in Zone 8a Kale in Zone 8a Garlic in Zone 8a Potatoes in Zone 8a Squash (winter) in Zone 8a Corn in Zone 8a Radishes in Zone 8a Beets in Zone 8a Eggplant in Zone 8a Basil in Zone 8a Cilantro in Zone 8a Parsley in Zone 8a Pumpkins in Zone 8a Sunflowers in Zone 8a

Frequently asked questions

When should I start onions in Zone 8a?

Start onions seeds indoors around Jan 14 (Zone 8a).

Can I direct sow onions in Zone 8a?

Onions is best started indoors and transplanted in Zone 8a rather than direct sown.

Can I plant onions in the fall in Zone 8a?

Yes. Plant onions between September 27 and October 18 in Zone 8a, roughly 6 to 3 weeks before the average first frost, so it roots before the ground freezes.

Will onions survive frost in Zone 8a?

Onions is a hardy crop and keeps going roughly 21 days past the first light frost in Zone 8a. A row cover or a straw mulch buys more.

How many plantings of onions fit in a Zone 8a season?

About 2. Zone 8a averages 228 frost-free days and onions needs roughly 100 days plus a couple of weeks of turnaround, so sowing every 57 days keeps a supply coming.