Ohio Planting Calendar: When to Sow and Plant, Frost Dates Included

Columbus’s last frost falls somewhere between May 5 and May 15, and that ten-day spread is the real decider behind every planting date in this calendar — not a single line to circle. Lake Erie’s shoreline holds its cool longer, pushing frost later; the Allegheny Plateau’s high ground traps cold air past when lowland gardens have relaxed; the Ohio River valley warms early. One number can’t hold all that, which is why it’s a starting point, not a guarantee.

The frost window in Ohio

Ohio State University Extension’s Ohio Gardening Calendar puts the last spring frost at Columbus, near the middle of the state, between May 5 and May 15 for hardiness zone 6a. That’s not a single date you can circle on the calendar. It’s a ten-day range built from years of temperature records, and in any given spring the actual last freeze could land anywhere inside it, or occasionally outside it.

Columbus sits in the middle of Ohio’s climate spread, and the rest of the state doesn’t share its number. Gardens near Lake Erie benefit from the lake’s slow release of stored heat in spring, which keeps the shoreline counties cooler in April and often pushes the last frost later than it runs at Columbus. Higher ground in the Allegheny Plateau and the hill country of the southeast holds cold air longer too, so a frost there can linger past the date a gardener an hour’s drive west has already stopped worrying about. Southwestern Ohio, along the Ohio River, tends to warm earlier in spring than the state average. None of this shows up in a single statewide number, which is exactly why the Columbus figure is a reference point, not a guarantee, for every county.

What the window means for your season

Everything else in this calendar is set relative to that window, not to a month on the wall. Cool-season crops go in before it closes. Warm-season crops wait until after it closes, and in most cases longer still, until the soil itself has warmed. The frost-free growing season in Ohio runs from whenever that spring window passes until the first hard freeze of fall, a date this page doesn’t have a sourced statewide figure for. OSU Extension’s county-level tables are the place to find that number for your own address, and it matters just as much as the spring date does, since it sets the far end of everything you plant this year.

Treat the May 5 to May 15 range as the earliest and latest edges of a transition, not as two separate options to pick between. A garden that gets a warm April can sometimes push its true last frost to the early end of that window, while a cold, wet spring can drag it toward the later end or past it. Watching your own soil and sky matters more than watching the date.

Cool-season crops

Peas, spinach, lettuce, brassicas and most root crops tolerate a light frost and actually perform better in cool soil than in heat, which is why they go into the ground before Columbus’s May 5 to May 15 frost window even closes. These crops germinate at lower soil temperatures than tomatoes or beans, and their leaves and roots hold up to a light freeze that would blacken a pepper seedling overnight.

What goes in first

• Peas and spinach: sown directly as soon as the soil can be worked, well before the frost window, since both germinate in cold ground and young plants shrug off a freeze.
• Lettuce and other salad greens: direct-sown or transplanted a few weeks ahead of the frost window, with successive small sowings rather than one big one.
• Brassica transplants (broccoli, cabbage, kale, Brussels sprouts): started indoors weeks earlier and set out as young plants ahead of the frost date, since a stocky transplant tolerates cold better than a direct-sown seedling.
• Root crops (carrots, beets, radishes, turnips): direct-sown ahead of the frost window, since they need to be sown in place and radishes in particular finish fast enough to be out of the ground before warm-season crops even go in.

The common thread is that none of these crops are waiting on the frost date the way a tomato is. They’re timed against the ground itself. A soil that can be raked into a seedbed without clumping is a soil cool-season seeds can germinate in, frost window or not. Pushing a sowing date later doesn’t help. Lettuce and spinach sown too close to the frost date hit summer heat before they’re through producing, and lettuce in particular bolts and turns bitter once the days warm.

Brassica transplants deserve a separate note, because the count-back math matters. A transplant that needs to go into the ground several weeks before the frost window has to be started from seed roughly six to eight weeks earlier still, which for Columbus’s window means starting trays well back in winter. Anyone transplanting brassicas after the frost window has already passed is effectively growing a summer crop instead of a spring one, and in Ohio’s summer heat, broccoli and cauliflower in particular tend to bolt or produce loose, poor heads.

Warm-season crops

Tomatoes, peppers, squash, beans and corn all die at the first touch of frost, so none of them go outside before Columbus’s frost window closes on May 5 to May 15. But the frost date alone understates how long these crops actually wait. Their seeds and roots need soil that has genuinely warmed, not just air that’s stopped freezing at night, and cold soil will rot bean seed and stall a tomato transplant even on a frost-free week. That’s why gardeners who transplant right at the edge of the frost window sometimes see slower growth than neighbors who waited another week or two for the soil to catch up.

Tomato varieties and their timing

Days-to-maturity figures on a seed packet are counted from the transplant date, not from seed, and they shift by a week or two either way depending on the season. Here’s how some common cultivars compare:

Count backward from that transplant point to know when to start seed indoors. Most tomatoes need six to eight weeks of growing time before they’re ready to go out, so counting six to eight weeks back from Columbus’s May 5 to May 15 window lands indoor sowing somewhere between early March and early April, earlier for gardeners further north who transplant later in the season. Add the days-to-maturity figure forward from the same window and you get harvest estimates too: Sakura or Sun Gold, planted right as the frost window closes, would mature sometime in the first half of July, while a long-season paste tomato like Amish Paste, planted on the same schedule, wouldn’t ripen until late July into early August. Both estimates shift with the weather and the exact transplant date, so treat them as planning ranges rather than promises.

Peppers follow roughly the same logic as tomatoes and are, if anything, less patient with cold soil. Squash, beans and corn are usually direct-sown, and because their seed simply won’t germinate in cold ground, most gardeners wait until the frost window has fully passed and the soil has had time to warm before putting seed in at all.

The fall planting window

Fall planting works backward from the first frost instead of forward from the last one, and this calendar doesn’t have a sourced first-fall-frost date for any single Ohio location. That date varies enough between the lakeshore, the hill country and the river valleys that a statewide or even a Columbus-only figure would mislead more than help. OSU Extension’s county-level frost tables are the place to get that number for your own garden before planning a fall crop.

How to work the math yourself

Once you have your first fall frost date, the calculation is straightforward. Take the days-to-maturity figure for the crop, add a margin of a couple of weeks to account for the shorter, cooler days of autumn slowing growth compared to the summer conditions the seed packet was tested under, and count that total backward From Your Frost date. The result is the latest safe sowing date for that crop. A fast root crop or a cut-and-come-again green needs far less lead time than a full head of cabbage, so it’s worth doing this math separately for each crop rather than picking one fall planting date for the whole garden.

Not every crop needs protecting from that first frost, either. Several fall vegetables improve with a light freeze:

• Kale turns sweeter as the plant converts starches to sugars in response to cold.
• Brussels sprouts firm up and sweeten after one or two light frosts.
• Carrots and parsnips left in the ground through a frost develop noticeably more sugar.
• Spinach sown for a fall crop tolerates a hard frost far better than it tolerates the summer heat it would have faced in spring.

That tolerance buys some flexibility spring planting doesn’t offer. A spring frost can wipe out a warm-season seedling with no warning and no recovery, but a fall frost on a cold-hardy crop is often the reason to leave it in the ground rather than the reason to pull it. Gardeners who treat the first frost as a hard deadline for harvesting everything in the plot are usually leaving flavor behind for crops built to handle the cold.

Reading a planting calendar properly

A statewide or even a Columbus-based planting calendar is a starting point, not an instruction sheet for your particular yard. Ohio’s geography is varied enough that two gardens sixty miles apart can run on genuinely different clocks, and a calendar built around one reference city can’t account for that.

What actually shifts the date

Elevation is one factor. Cold air sinks, so a garden at the bottom of a slope or in a low valley often sees frost when a garden on higher ground nearby does not, on the same night. Lake Erie’s shoreline counties get the opposite effect in spring, staying cooler longer as the lake releases the previous season’s warmth slowly, which delays the last frost compared to inland Ohio. Cities create their own microclimate too. Pavement and buildings hold heat, so a downtown garden in Columbus, Cincinnati or Cleveland often runs a few days to a week ahead of an open field on the same latitude just outside town. None of that shows up in a single date on a chart.

A late cold snap can also override the calendar entirely, regardless of where you garden. A frost window is built from historical averages, and averages don’t rule out an outlier year where a hard freeze arrives after the window has technically closed. Watching the actual forecast in the two weeks around your expected frost date matters more than trusting the average once you’re inside that window.

The most reliable fix is to start keeping your own record. Note the date of the last frost you actually see in your yard each spring, log the soil temperature when you plant, and after two or three seasons you’ll have a more useful calendar than any statewide chart, calibrated to your own microclimate. For more on how these regional differences play out across the rest of the state, our Ohio guides break conditions down beyond the Columbus reference point used here.

Local help

Every date on this page is built around Columbus, and Ohio is too large and too varied for one reference city to serve every county well. OSU Extension maintains county offices across the state with local frost data, soil testing services and planting guidance calibrated to your own ground rather than to the state capital. Find your county’s office and request a soil test before you plant this spring. Start at the Ohio State University Extension website, and ask specifically for the frost data and soil test options.

Common questions

What zone is Ohio in for planting?

Most of the state falls in USDA hardiness zones 6a and 6b, with small pockets running a half-zone cooler or warmer depending on elevation and proximity to Lake Erie. The Columbus reference point used throughout this page is zone 6a, per OSU Extension’s Ohio Gardening Calendar, but check your own zone before ordering perennials or fruit trees that depend on it.

Can I plant tomatoes before the last frost if I cover them?

A row cover or wall of water can get you a week or so of head start, but it protects against light frost only, not a hard freeze, and it does nothing to warm the soil itself. Most gardeners find the earlier planting date isn’t worth much if the roots are still sitting in cold ground.

I missed the spring planting window. Is it too late?

For warm-season crops like tomatoes and peppers, a late start usually still finishes before fall frost given Ohio’s frost-free stretch, though you’ll want to lean toward a shorter-season cultivar rather than a long-season paste tomato. For cool-season crops like spinach or lettuce, a late spring sowing often runs into summer heat and bolts, so it’s usually better to wait and plant that crop again in late summer for a fall harvest instead.

Do I need to start every warm-season crop indoors?

No. Squash, beans and corn are usually direct-sown once the soil has warmed and the frost window has passed, since they grow fast enough from seed that transplanting offers little advantage and their roots often resent being disturbed. Tomatoes and peppers are the crops most worth starting indoors, since their long days-to-maturity figures need a head start Ohio’s season doesn’t otherwise give them.

How do I find the actual frost date for my county instead of Columbus’s?

OSU Extension’s county offices keep local frost and climate records that go well beyond the single Columbus figure used as a reference point here. Contact your county extension office directly, since a gardener in a lakeshore county or up in the hill country can be working with a meaningfully different date than the one this page opens with.