Onions are cool-season crops, so it’s no surprise that they’re hardy enough for Ohio’s zone 5 and zone 6. Within the state, it’s possible to grow onions in both spring and fall, provided you get the timing right.
So when to plant onions in Ohio? You can grow them outdoors in April and May or around August and September, whether it’s seeds, sets, or transplants you’re using. Note that your frost dates can influence these estimates.
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When to Grow Onions in Ohio
Without further ado, follow these guidelines to grow onions in Ohio:
- Plant onion sets outdoors after the last frost. As you do this, the temperature should measure above 28℉ at the minimum, with the optimal range being 55 to 75 degrees.
- For those who use seeds instead, sow them indoors four to six weeks before the final frost, then move the seedlings or transplants outside after it. Note that seeds may not germinate if they’re older than a year, which is why it’s essential to use fresh seeds only.
- Later in the fall, plant onion sets in garden four to six weeks before the first frost. If you’d rather use seeds for whatever reason, sow them eight to ten weeks before freezing weather arrives.
In Cleveland or northeast Ohio, for instance, the planting dates would be September 26 to October 10 for sets and August 29 to September 12 for seeds, provided the first frost falls on November 7.
While planning your schedule, it’s also wise to consider what types of onions you should grow.
Different onion types require varying hours of sunlight to form bulbs, with long-day varieties demanding the highest amount of daylight, followed by intermediate and short-day varieties (the requirements are 16 hours vs. 14 hours vs. 12 hours, to be specific).
Since Ohio comprises hardiness zones 5 and 6, intermediate and long-day onions will work best here. Short-day cultivars may also thrive in the state, but you must grow them in late winter.
Onion varieties aside, here are the frost estimates for some regions in the Buckeye state. You can use the first and last frost date Dayton Ohio plus other areas have to determine your gardening schedule.
|Location||Final frost||First frost|
|Athens||May 1||October 16|
|Brook Park||April 27||October 30|
|Columbus||April 27||October 20|
|Dayton||April 25||October 21|
|Findlay||April 29||October 19|
|Lancaster||April 30||October 18|
|Newark||May 5||October 10|
|Portsmouth||April 24||October 19|
|Toledo||April 27||October 22|
Best Onions to Grow in Ohio
Before growing onions from bulbs or transplants, consider the following varieties, which suit Ohio’s climate well.
|Categorization||Name||Great for||Other attributes|
|Long-day||Early Yellow Globe||Bunching – you can harvest both the greens and the bulbs of these varieties.||Best grown from seeds
These yellow onions will complement salsas and stir-fried dishes. They have considerably long storage as well.
|White Sweet Spanish||Best grown from transplants
These white onions have a sweet, mild taste, ideal for people who don’t want their herbs to be too pungent.
|White Spear||White onions that grow best from seeds and in raised beds with compost
Has excellent heat resistance
|Ebenezer||Grow from sets and are ideal for storage
These yellow onions produce harvestable greens within four weeks and bulbs within 85 days.
|Sweet Sandwich||Storing||Yellow onions that grow well from sets, have good resistance to mildew and are somewhat frost-hardy|
|Walla Walla||Sweet white/yellow onions that grow best from transplants
Edible for up to two months after harvest
|Yellow Sweet Spanish||Sweet yellow onions suitable for transplanting
Have a crunchy texture and high yield
|Intermediate||Candy||Moderately sweet and pungent white onions, great in slaws, salsas, glazes, and roasts
Cultivable through all mediums (seeds, sets, transplants)
|Super Star||Producing big bulbs||Sweet, mild onions with white coloring
Grow well from seeds
How late can I plant onions in Ohio?
You can plant onion bulbs as late as September, though it’s best to look up the first frost where you live and count backward four to eight weeks to determine the latest sowing date. Four weeks of frost-free weather are necessary for sets, while seeds will require at least eight weeks.
Can I plant onions in the fall in Ohio?
Yes. As mentioned above, planting onions in the fall in OH is possible. As long as your seeds or sets have enough time to establish themselves before winter, they will enter dormancy during the cold season and resume growing in spring.
When to harvest onions in Ohio?
Onions will mature within 90 to 120 days, so expect to collect them around the end of June to July, with September being the latest month. If your plants have soft necks, floppy tops, and 100% dried leaves, they’re ready for harvesting.
Deciding when to plant onions in Ohio is straightforward. All you need is your calendar, some basic math skills, the frost dates of your city, and you’re good to go.
Just as importantly, remember to pick the appropriate onion variety for your climate, and send us any questions if you have them.
Until then, have a nice day!
Planting schedule in Ohio for other vegetables: