Root Vegetable

When to Plant Onions in Ohio

The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.

The Short Answer

Ohio grows excellent onions — the state sits firmly in long-day onion territory, and the moderate growing season provides enough time for full-size bulbs. Starting onions from sets, transplants, or seed each has advantages, but transplants produce the largest, most uniform bulbs in Ohio's conditions.

Ohio Frost Dates

Your planting dates depend on which part of Ohio you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Ohio 5b, 6a May 1 - May 15 Oct 1 - Oct 15
Central Ohio 6a, 6b Apr 20 - May 5 Oct 10 - Oct 25
Southern Ohio 6b Apr 15 - Apr 30 Oct 15 - Oct 30

Onions Planting Schedule for Ohio

Northern Ohio (Zones 5b, 6a)

Average last frost: May 1 - May 15 · Average first frost: Oct 1 - Oct 15

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Central Ohio (Zones 6a, 6b)

Average last frost: Apr 20 - May 5 · Average first frost: Oct 10 - Oct 25

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Southern Ohio (Zones 6b)

Average last frost: Apr 15 - Apr 30 · Average first frost: Oct 15 - Oct 30

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Growing Onions in Ohio

State-Specific Growing Tips

Plant onion sets or transplants 4 weeks before last frost (early to mid-April). For the largest bulbs, start onions from seed indoors 10 weeks before last frost (late January to early February) — this requires patience but produces superior results. Ohio is long-day onion territory — bulbing is triggered by 14-16 hours of daylight, which occurs in June. Plant in well-drained soil amended with compost. Stop watering when tops begin to fall over, signaling maturity. Cure in a warm, ventilated area for 2-3 weeks before storage.

Recommended Varieties for Ohio

Long-day varieties only in Ohio: Walla Walla (sweet, poor storage), Copra (excellent storage), Yellow Globe Danvers. Red varieties: Red Zeppelin, Redwing. Ohio State Extension recommends Copra for storage and Walla Walla for fresh eating.

Common Challenges in Ohio

Onion maggot damages bulbs — use floating row cover over seedlings. Thrips cause silvery streaks on leaves — insecticidal soap. Neck rot during wet growing conditions. Downy mildew and purple blotch in humid summers.

Growing Tips

Day length triggers bulbing. Northern gardeners need long-day varieties. Southern gardeners need short-day varieties.

Companion Planting

Plant onions alongside these companions for better growth:

Carrots Lettuce Beets Tomatoes

Keep onions away from:

Beans Peas

The Bottom Line

Onions can be grown successfully in Ohio with proper attention to regional frost dates and local growing conditions. Timing varies across the state — Northern Ohio gardeners work with a last frost around May 1 - May 15, while Southern Ohio sees frost end around Apr 15 - Apr 30. Choose varieties suited to your region, amend your soil based on its specific needs, and monitor for the pests and diseases most common in your area. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Onions Growing Guide National planting guide with all states Ohio Planting Calendar All plants for Ohio Onions in Alabama Alabama planting dates Onions in Alaska Alaska planting dates Onions in Arizona Arizona planting dates Onions in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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