When to plant · 31 cities · zones 6a–7a
When to plant onions in Ohio
Start Spanish Onion seeds indoors around Jan 30 and transplant around Mar 27 — the Ohio statewide median, counted from a last spring frost of Apr 24 across 1,178 ZIP codes and 140 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
Ohio onions, by step
Statewide median last frost Apr 24, first fall frost Oct 22, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.
| Cultivar | Start indoors | Plant out | First harvest | Days |
|---|---|---|---|---|
| Spanish OnionYellow Sweet Spanish (long-day) | Jan 30 | Mar 27 | Jul 15 | 110 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station Ohio's ZIP codes resolve to.
Onions in Ohio, city by city
Spanish Onion, scheduled from each city's nearest NOAA station — the same dates as its frost page.
| City | Last frost | Start indoors | Plant out | First harvest |
|---|---|---|---|---|
| Columbuszone 6b | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Clevelandzone 7a | Apr 8 | Jan 14 | Mar 11 | Jun 29 |
| Cincinnatizone 6b | Apr 16 | Jan 22 | Mar 19 | Jul 7 |
| Toledozone 6b | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Akronzone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Daytonzone 6b | Apr 18 | Jan 24 | Mar 21 | Jul 9 |
| Parmazone 6b | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Cantonzone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Lorainzone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Hamiltonzone 6b | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
| Youngstownzone 6a | May 1 | Feb 6 | Apr 3 | Jul 22 |
| Springfieldzone 6a | Apr 25 | Jan 31 | Mar 28 | Jul 16 |
| Ketteringzone 6b | Apr 18 | Jan 24 | Mar 21 | Jul 9 |
| Elyriazone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Middletownzone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Newarkzone 6a | Apr 29 | Feb 4 | Apr 1 | Jul 20 |
| Cuyahoga Fallszone 6b | Apr 24 | Jan 30 | Mar 27 | Jul 15 |
| Lakewoodzone 7a | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Dublinzone 6b | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
| Euclidzone 7a | Apr 8 | Jan 14 | Mar 11 | Jun 29 |
| Beavercreekzone 6b | Apr 18 | Jan 24 | Mar 21 | Jul 9 |
| Mansfieldzone 6a | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
| Mentorzone 7a | Apr 26 | Feb 1 | Mar 29 | Jul 17 |
| Delawarezone 6b | Apr 19 | Jan 25 | Mar 22 | Jul 10 |
| Strongsvillezone 6b | Apr 20 | Jan 26 | Mar 23 | Jul 11 |
| Fairfieldzone 6b | Apr 19 | Jan 25 | Mar 22 | Jul 10 |
| Cleveland Heightszone 6b | Apr 8 | Jan 14 | Mar 11 | Jun 29 |
| Grove Cityzone 6b | Apr 23 | Jan 29 | Mar 26 | Jul 14 |
| Huber Heightszone 6b | Apr 16 | Jan 22 | Mar 19 | Jul 7 |
| Reynoldsburgzone 6b | Apr 18 | Jan 24 | Mar 21 | Jul 9 |
| Lancasterzone 6a | Apr 22 | Jan 28 | Mar 25 | Jul 13 |
What these onions become
What Ohio onions need
Yellow Sweet Spanish Onion Seed
A long-day storage onion with enough sugar to sweat down without scorching. The aromatic base under every tomato sauce on this site.
Organic Seed Starter Potting MixMust have
Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.
72-Cell Trays with 1020 Bottoms, 5-PackMust have
The cheap black nursery trays crack after one season and flex enough to break roots when you lift them. These do not. Over five seasons the price per use is lower than the throwaways.
T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have
A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.
Rapitest Soil Test Kit
In-ground growers are guessing until they test. pH outside 6.0–6.8 locks nutrients out no matter how much fertiliser you add, and no amount of feeding fixes that.
Pure Organic Worm Castings, 15 lb
Not a fertiliser so much as a soil-biology inoculant with a mild nutrient charge. A cup in each planting hole is a cheap, unglamorous improvement you can measure by August.
Garden Harvest Basket with Tool Caddy
A harvest basket that doubles as a colander means the hose rinse happens in the garden, and the dirt stays outside. On a 20-pound tomato day that is a genuine time saving.
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Onions in Ohio: questions
When should I plant onions in Ohio?
Transplant around Mar 27 at the statewide median; across the state that date runs from Mar 20 in the warmest tenth of Ohio's ZIP codes to Apr 3 in the coldest. To cut the freeze risk to one year in ten, count from May 10 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Ohio?
Around Jan 30 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Ohio?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 24. In the warmest tenth of Ohio's ZIP codes the median last frost falls on or before Apr 17; in the coldest tenth, on or after May 1.
When will Ohio onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jul 15: 110 days from transplant.
Which onions grow in Ohio?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every Ohio city listed here is north of that line.
More for Ohio
- When to plant tomatoes
- When to plant peppers
- When to plant tomatillos
- When to plant basil
- When to plant cilantro
- When to plant carrots
- When to plant mustard greens
Onions in every state → · Ohio frost dates → · How frost-date math works →