Plant Onions in Zone 8b

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

Start indoors

Jan 4

Transplant

Mar 1

Harvest (~100d)

Jun 9

Zone 8b averages 245 frost-free days, running from a last spring frost around March 15 to a first fall frost around November 15. Onions needs roughly 100 days from planting out to first harvest, so it uses about 41 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 4, about 10 weeks ahead of the Zone 8b last frost. Transplants go out around Mar 1. Starting earlier than that in Zone 8b usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 100 days to harvest, a 245-day Zone 8b season has room for about 2 sowings, so stagger them rather than planting everything at once.

Planting onions for a fall harvest in Zone 8b

Yes. Plant onions between October 4 and October 25 in Zone 8b, 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

Oct 4

Plant by

Oct 25

Overwinters, harvest in spring

Spring

Fall dates are counted backward from the Zone 8b 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 8b

Planting	Sow or start	In the ground	Harvest
Spring	Jan 4	Mar 1	Jun 9
Fall	by Oct 25	Oct 25	Next spring

Last spring frost

Mar 15

First fall frost

Nov 15

Growing season

245 days

Onions in nearby zones

Onions in Zone 8a (colder) Onions in Zone 9a (warmer) Full Onions grow guide Zone 8b planting calendar

Other crops in Zone 8b

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

Frequently asked questions

When should I start onions in Zone 8b?

Start onions seeds indoors around Jan 4 (Zone 8b).

Can I direct sow onions in Zone 8b?

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

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

Yes. Plant onions between October 4 and October 25 in Zone 8b, roughly 6 to 3 weeks before the average first frost, so it roots before the ground freezes.

Will onions survive frost in Zone 8b?

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

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

About 2. Zone 8b averages 245 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.