Plant Onions in Zone 5a

Seed-starting, transplant & harvest dates for USDA Zone 5a

Start indoors

Feb 19

Transplant

Apr 16

Harvest (~100d)

Jul 25

Zone 5a averages 156 frost-free days, running from a last spring frost around April 30 to a first fall frost around October 3. Onions needs roughly 100 days from planting out to first harvest, so it uses about 64 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 Feb 19, about 10 weeks ahead of the Zone 5a last frost. Transplants go out around Apr 16. Starting earlier than that in Zone 5a usually backfires: plants outgrow their cells and stall when they finally hit cold soil.

Planting onions for a fall harvest in Zone 5a

Yes. Plant onions between August 22 and September 12 in Zone 5a, 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

Aug 22

Plant by

Sep 12

Overwinters, harvest in spring

Spring

Fall dates are counted backward from the Zone 5a 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 5a

Planting	Sow or start	In the ground	Harvest
Spring	Feb 19	Apr 16	Jul 25
Fall	by Sep 12	Sep 12	Next spring

Last spring frost

Apr 30

First fall frost

Oct 3

Growing season

156 days

Onions in nearby zones

Onions in Zone 4b (colder) Onions in Zone 5b (warmer) Full Onions grow guide Zone 5a planting calendar

Other crops in Zone 5a

Tomatoes in Zone 5a Peppers in Zone 5a Cucumbers in Zone 5a Lettuce in Zone 5a Zucchini in Zone 5a Carrots in Zone 5a Beans (bush) in Zone 5a Peas in Zone 5a Broccoli in Zone 5a Spinach in Zone 5a Kale in Zone 5a Garlic in Zone 5a Potatoes in Zone 5a Squash (winter) in Zone 5a Corn in Zone 5a Radishes in Zone 5a Beets in Zone 5a Eggplant in Zone 5a Basil in Zone 5a Cilantro in Zone 5a Parsley in Zone 5a Pumpkins in Zone 5a Sunflowers in Zone 5a

Frequently asked questions

When should I start onions in Zone 5a?

Start onions seeds indoors around Feb 19 (Zone 5a).

Can I direct sow onions in Zone 5a?

Onions is best started indoors and transplanted in Zone 5a rather than direct sown.

Can I plant onions in the fall in Zone 5a?