Plant sweet potato slips in Ohio once the last frost has passed and the soil has warmed, which puts planting after the May 5 to May 15 frost window, not inside it. The crop sits out a cool spring, uses most of the summer, and has to be out of the ground before fall frost arrives, October 5 to October 15 in zone 6a.
When the soil is warm enough in Ohio
The last spring frost in Ohio falls between May 5 and May 15 in zone 6a, according to the Ohio State University Extension Ohio Gardening Calendar. Treat that window as the day the calendar starts to matter, not the day to plant. A frost date is a probability, not a promise, so a cold night after it should not shock anyone.
Frost is a stand-in for the real signal
Sweet potatoes come from the tropics and relate to morning glories. They don’t wait for frost to end. They wait for warm soil, and soil warms after the frost risk ends, not along with it. A May afternoon can hit 70 F in the air while the ground a few inches down is still holding the chill of a wet April. Slips set into that ground stall, the leaves yellow or turn purplish, and on cold wet soil the stems can rot before roots ever take hold.
Soil type changes the lag. Heavy, wet clay warms slowest. A raised ridge drains faster and warms sooner, and black plastic laid over it for a couple of weeks before planting adds more. Pushing a soil thermometer to planting depth each morning beats any calendar. Plant when the readings hold warm for several mornings in a row, not after one sunny weekend. Your state extension service can give the threshold temperature it recommends.
The frost dates above belong to zone 6a. Ohio spans USDA hardiness zones 5b to 6b (USDA Plant Hardiness Zone Map, 2023, built on average annual extreme minimum temperature), so a garden in a colder pocket of the state will see its last frost later than a garden near Columbus. Let your own spring record override the statewide number.
Not a yam, not a potato
The supermarket label “yam” is wrong for sweet potatoes. True yams are a different tropical plant entirely. A sweet potato is also not a potato. It isn’t a nightshade, so the usual worry about rotating it with potatoes, tomatoes and peppers doesn’t apply. Rotation matters against other sweet potatoes. Putting the crop back into the same bed year after year invites soil-borne trouble, so give it a different spot each season.
That difference also explains the planting method. Potatoes go in as seed pieces in cool soil. Sweet potatoes go in as rooted or unrooted cuttings called slips, in warm soil, well after the cool-season crops have been planted.
How long the season lasts here
Count the days between the dates and Ohio’s frost-to-frost season in zone 6a comes out between 143 and 163 days, depending on which ends of the two ranges you pair. Matching the earliest last frost with the earliest first frost, or the latest with the latest, gives 153 days either way.
| Pairing | Last spring frost | First fall frost | Days between |
|---|---|---|---|
| Short end | May 15 | October 5 | 143 |
| Early with early | May 5 | October 5 | 153 |
| Late with late | May 15 | October 15 | 153 |
| Long end | May 5 | October 15 | 163 |
Those numbers overstate what a sweet potato gets. Slips can’t go out on the last frost day, because the soil is still cold. The real working window is shorter than the frost-to-frost count by however long your ground takes to warm, which in a wet spring can be a couple of weeks or more.
What that length allows
One planting. A window that long, then trimmed at the front, leaves no room for a true second sowing in midsummer, because slips set out in July would meet fall frost before the roots had bulked up. Staggering slips over a week or so can spread out the work and hedge against a cold snap, but it is not a second crop. Gardeners who like succession planting can still use it for quick crops that finish before the sweet potato bed needs the space. The succession sowing guide on this site covers how to time those.
The fall end of the window
The first frost, October 5 to October 15, blackens the vines. Cold soil can also injure the roots below, so the harvest should be planned ahead of that date and not left to chance. Dig on a dry day, handle the roots gently because the skin bruises easily, and don’t wait for the weather to decide. Keep a close eye on the forecast in the first half of October.
Heat and water in Ohio
Columbus averages 15.3 days a year at 90 F or more, based on NOAA NCEI Climate Normals for 1991-2020. That is a count at one reference station, not a description of every Ohio backyard, but it tells you plenty about the crop. Sweet potatoes want accumulated warmth and warm nights, not just a few hot afternoons. Growers in Florida, where the heat is long and steady, can plant and mostly step back, as described in Growing Sweet Potatoes in Florida. An Ohio gardener builds the warmth: plastic over the bed, ridges to warm and drain the soil, and a type chosen for an early finish.
If the summer runs cool and damp
A cool, wet summer is the failure to plan for. Vines grow lush while roots bulk slowly. Mildew and other foliar disease move through crowded, damp leaves, and the crop ripens late, running into the October frost window with roots still small. A summer like that rewards plastic, ridges and an early type, and punishes a bed planted in cold, soggy ground. Gardeners in the neighboring state can compare notes in Growing Sweet Potatoes in Pennsylvania, where gardeners face a similar balance between heat and cool, damp spells.
Rain, soil and splitting
Summer rainfall at the same station totals about 12.7 inches across June, July and August, out of 41.6 inches for the year. Month by month it runs 4.33 inches in June, 4.67 in July and 3.74 in August, the driest of the three (NOAA NCEI Monthly Climate Normals 1991-2020, station USW00014821). Those are normals, what the region can usually expect, not a forecast.
Even moisture lets roots swell steadily. A long dry stretch followed by a downpour is what splits them near the end of the season. So the same inches of rain can mean different things in different beds. On clay, rain lingers for days and a bed can stay soggy, which is where ridges earn their keep. On sandy ground, rain drains within the day and the bed may need watering even in a wet month.
A rain gauge on your own plot settles the question better than any normal. Water deeply when the gauge and the soil both say the week has been dry. Ease off as harvest approaches, because a heavy soaking onto dry ground late in the season is when splitting is most likely.
The wider method, from slips to heat to curing, is laid out in Growing Sweet Potatoes: Slips, Heat, and a Careful Cure.
Which sweet potatoes suit Ohio
Choose by type, and let Ohio’s conditions pick the type. A 143 to 163 day frost-to-frost season, trimmed by a slow-warming spring, favors the earliest-maturing types over the late, big-rooted ones that need a long, hot summer. Only 15.3 days at 90 F means you shouldn’t count on the weather to do the work for a heat-loving type. And about 12.7 inches of summer rain, with humid spells and plenty of clay, makes disease resistance the first thing to look for on a slip order.
| Ohio condition | What it favors |
|---|---|
| Frost-to-frost season of 143 to 163 days, shortened by cold spring soil | The earliest-maturing types, planted on warmed ridges |
| 15.3 days a year at 90 F or more (Columbus) | Plastic, ridges and early types instead of relying on summer heat |
| About 12.7 inches of rain from June through August, often on clay | Disease-resistant types, good airflow between plants, well-drained beds |
The only recommendation worth following is the one backed by trials in Ohio soil and Ohio summers, and a name borrowed from another climate can steer you wrong. Ohio State University Extension and your county office know which varieties have been grown and evaluated near you, and they can tell you which slip suppliers the local gardeners trust. Ask them for the types that performed in a short, cool-leaning season, and take a list to the nursery or the online order form.
After the dig, store with care
Curing and storage deserve caution, because a good harvest can still be ruined afterward. Cold is the main danger. Never store sweet potatoes in a refrigerator or a cold cellar. Cold injury below the proper storage range is real and permanent, and it is the most common way a home crop is lost after a good harvest. A root hurt by cold may look fine for days, then turn hard in the center or rot.
Inspect every root and every box. Look for soft patches, sunken spots, mold, or any weeping, sticky spot. One of those ends the question for that root, and a root that looks sound on the outside is not proof that it is fine inside. Check the stored roots regularly, pull out any that are going bad, and cook the nicked or bruised ones first.
Common questions
When should I plant sweet potato slips in Ohio?
After the last frost window, May 5 to May 15 in zone 6a, and after the soil has warmed. Use a soil thermometer at planting depth in the morning, and wait until the readings stay warm for several days. Air temperature alone misleads because soil trails behind it.
Can I grow sweet potatoes in northern Ohio or a colder part of the state?
Often yes, with more care. Ohio runs from USDA zone 5b to 6b, and the dates above belong to zone 6a. A colder spot has a later last frost and an earlier first frost, so the season is shorter. Early-maturing types, black plastic and warmed ridges matter more there. Your county extension office can say which types have done well near you.
Should I rotate sweet potatoes with potatoes and tomatoes?
That rotation rule doesn’t apply. A sweet potato isn’t a nightshade and is only a distant relative of potatoes in name. What matters is not planting sweet potatoes in the same bed year after year, which lets soil problems build up.
Can I keep harvested sweet potatoes in the refrigerator?
No, and neither in a cold cellar. Cold injury is irreversible, and the damage often shows up only later as rot or a hard core. Cure and store them warm and dry, well above refrigerator temperatures, check them regularly, and remove any root with a soft or weeping spot.