When to Plant Onion in Ohio
Start Seeds Indoors
Friday, February 13, 2026
Transplant outdoors: Friday, April 24, 2026
State
Ohio
USDA Zones
5b, 6a, 6b, 7a
Avg Last Frost
Friday, April 10, 2026
Cities Covered
1059
Ohio Planting Schedule by Zone
Ohio spans 4 zones — find yours below for the most accurate dates.
| Zone | Last Frost | Start Indoors | Transplant |
|---|---|---|---|
| 5b | Saturday, April 25, 2026 | Saturday, February 28, 2026 | Saturday, May 9, 2026 |
| 6a | Monday, April 20, 2026 | Monday, February 23, 2026 | Monday, May 4, 2026 |
| 6b | Wednesday, April 15, 2026 | Wednesday, February 18, 2026 | Wednesday, April 29, 2026 |
| 7a | Friday, April 10, 2026 | Friday, February 13, 2026 | Friday, April 24, 2026 |
Dates based on average last frost. Check your local forecast before planting.
🌿 About Onion
🤝 Companion Plants for Onion
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Growing Onion in Ohio: Complete Guide
Onion (Allium cepa) is a warm-season crop that needs a head start indoors before Ohio's last frost. Most Ohio gardeners begin seeds indoors around Friday, February 13, 2026 and move transplants outside around Friday, April 24, 2026, after the risk of frost has passed.
Because Ohio stretches across 4 USDA hardiness zones (5b, 6a, 6b, 7a), planting windows can shift by as much as two to four weeks from one end of the state to the other. Gardeners in the warmer southern zones can start earlier, while those in cooler northern zones should wait until the zone table above shows their last frost has passed.
With 100 days to maturity, Onion needs the indoor head start that Ohio's growing season requires. Starting indoors ensures you have strong transplants ready the moment outdoor conditions are right.
Onion requires full sun (6+ hours) and moderate moisture. Most of Ohio receives adequate sunlight during the growing season, though gardeners in humid eastern regions should watch for fungal issues and ensure good air circulation.
For the most precise planting dates tailored to your exact location, enter your ZIP code on our planting calendar or use the zone table above to find the schedule for your area of Ohio.
Growing Onion in Ohio: Local Tips
Climate-specific advice for Ohio gardeners.
Long-day varieties, planted early
Plant sets or transplants as early as the soil can be worked (March in most of the Midwest); onions need the full season to size up before the long summer days trigger bulbing.
Frequently Asked Questions
When should I plant Onion in Ohio?
In Ohio, start Onion seeds indoors around Friday, February 13, 2026 and transplant outdoors around Friday, April 24, 2026 after your last frost. Ohio spans zones 5b–7a, so dates shift by 1–4 weeks depending on where you live.
What is the last frost date in Ohio?
Ohio spans 4 USDA zones (5b, 6a, 6b, 7a), so last frost dates vary by region. Sparta (5b) sees frost until around Saturday, April 25, 2026, while Cleveland, Lakewood, Rocky River (7a) is frost-free much earlier.
How long does Onion take to grow in Ohio?
Onion takes about 100 days from transplant (or direct sow) to harvest. Starting seeds indoors in Ohio gives you a head start so plants are ready to go out after the last frost.
What USDA zones does Ohio cover for Onion?
Ohio includes zones 5b, 6a, 6b, 7a. Onion grows well across all of these zones with adjusted timing — use the zone table above to find the right dates for your part of the state.
Find Precise Dates for Your City
Select a city for exact planting dates based on local frost records.