Set sweet potato slips in the ground after the last light frost has passed and the soil has warmed, which at the Little Rock reference station means after April 3. Plan to dig the crop before the first light frost on October 31.
The short answer for Arkansas
Plant sweet potato slips in late spring, after April 3 and once the soil feels warm to your hand. Harvest before October 31, the light-frost date at the 36F threshold from the National Weather Service in Little Rock. That gives the crop a long, hot stretch in between, and Arkansas summers are well suited to it. The mean 32F freeze dates are a wider band, and they matter less here.
What are the March 12 to March 28 dates a probability of?
NOAA’s 1991-2020 Climate Normals for the Little Rock station (USW00013963) give a band of dates for the last spring freeze at 32F. From March 12 to March 28, the chance of one more freeze is between 30 and 70 percent. Before March 12 a freeze is more likely than not. After March 28 it becomes less likely, though it never drops to zero. In fall the same band runs from November 7 to November 20 for the first 32F freeze.
These are 30-year normals at one reference station. They describe what the region can usually expect and do not predict any single spring. Some years the last freeze comes in early March, and some years it comes in April.
Which frost date should sweet potatoes follow?
Sweet potatoes are tropical in origin. The leaves are damaged by a light frost, and the roots stall in cold soil well before the air reaches 32F. For tender plants like these, the 36F dates are the useful ones: April 3 in spring and October 31 in fall. Planting on March 28 because the freeze odds have just dropped below half would put slips into cold ground, with another frost still possible.
The practical rule is simple. Wait until after April 3, then wait a little longer for warm soil. A slip set into warm ground puts out roots within days and starts running. A slip set into cold ground sits there and can rot. Most Arkansas gardeners set slips well after that date, in late spring, because the crop has plenty of runway. Summer heat is reliable, with an average of 69.2 days a year reaching 90F or more at the reference station. Sweet potatoes thrive on that heat, so there is no reason to rush.
For variety choices that fit this window, see The Best Sweet Potatoes to Grow in Arkansas. For the full growing picture from slips to curing, start with Growing Sweet Potatoes in Arkansas.
What will not work here
Three planting mistakes fail repeatedly in a climate with this much rain, this much heat, and a fall frost that arrives at the end of October. Each one comes from borrowing a calendar from somewhere else, or from treating the 32F dates as a green light.
Why does early planting fail?
The most common error is planting by the freeze dates. A gardener sees March 12 to March 28 and decides spring has arrived. The band says there is still a real chance of a freeze, and the light-frost date of April 3 is later still. Even with no frost at all, soil in March and early April is cool and often wet. Slips set into it do not grow. They sit, and the wet ground invites rot. A slip planted two weeks too early usually ends up behind one planted two weeks late.
Why do slow varieties fail when planted late?
The opposite mistake is planting very late with a variety that needs a long season. The light-frost date of October 31 sets the end of the growing window. Packet days to harvest for sweet potatoes count from transplanting. If you set slips in late June and the tag says a long stretch of days, the roots will still be small when the vines blacken. Late planting works only with quicker varieties, so check the tag before you plant.
Do weekly watering and close spacing work here?
Summer rain at the reference station adds up to about 10.0 inches across June, July, and August: 3.55 in June, 3.33 in July, and 3.16 in August, the driest month. Over the whole year the total is 50.4 inches. That sounds generous, but summer rain often arrives as a single thunderstorm that runs off, and the 69.2 days at or above 90F pull moisture out of the soil fast. On sandy ground, a gardener who waters once a week can watch the vines wilt by midweek. A rain gauge on your own plot tells you what actually landed.
Clay soil goes the other way. It holds a storm’s rainfall for days, and then a humid stretch keeps the ground wet around the roots. Crowded vines trap that humidity under the leaf canopy, and the roots crack or rot. Give each slip room, and let air move through the row. A wet clay bed does better as a raised, loosened ridge than as flat ground.
What changes across Arkansas
Arkansas is not one garden. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) runs from 6b to 8a across the state. That zone system rests on one variable, the average annual extreme minimum temperature. It says how cold winters get and says little about summer heat or rainfall, so use it as a rough guide to how far a calendar can shift.
The frost dates in this article come from the Little Rock reference station in the center of the state, and they are the starting point. A gardener in the cooler northern counties and the higher ground of the Ozarks and Ouachitas should expect a later last frost in spring and an earlier first frost in fall. Both changes shrink the growing window. A gardener in the warmer southern and southeastern parts of the state can expect the opposite, with a longer window on both ends.
For someone in the north or at altitude, the adjustments are practical ones:
- Wait longer in spring before setting slips, and let the soil warm fully.
- Favor varieties that mature faster, since the fall frost may come earlier than the Little Rock date.
- Plan to dig early if a frost forecast shows up, instead of waiting for the end of October.
- Consider black plastic over the bed in spring to warm the soil sooner.
Where to check this for your own county
The University of Arkansas System Division of Agriculture Cooperative Extension Service has an office in every county, and the local agents know what grows in the soil near you. Ask them for two things.
The first is the local planting calendar for sweet potatoes, or for warm-season vegetables if that is what they publish. It will show the dates that work in your county, which may differ from the Little Rock ones by a week or two in either direction. The second is the list of varieties that have been trialed near you. Variety performance depends heavily on soil and season length, and a variety that does well in the Delta may struggle in the hills.
The dates in this article are a state-level starting point drawn from a single reference station. If the county agent’s date and the date here disagree, go with the agent’s.
Checking this against your own garden
Your own observations outrank every date in this article. Three signs are worth watching, and none needs equipment.
Soil warmth by feel. Push your hand a few inches into the bed in the morning. If it feels cool and clammy, wait. If it feels like the inside of a house on a mild day, the ground is ready.
Weeds are the second sign. When crabgrass and other warm-season weeds start sprouting in your yard, the soil has warmed. If they come up first along a south-facing wall and weeks later in the shaded beds, you have just mapped the microclimates in your own yard.
The third sign is the slips themselves. A week or two after planting, a healthy slip pushes out a fresh leaf at the tip. That leaf means roots have taken. If the tip yellows or the slip stays flat for more than a couple of weeks, the soil was likely too cool or too wet. Replant if you have to. Plenty of season remains.
The Moon calendar is a separate, older custom: see when to plant sweet potatoes by the moon, written as tradition rather than fact.
Common questions
Can I plant sweet potatoes in March?
No. March sits inside the freeze-probability band for the Little Rock station, and the light-frost date is April 3. Cold, wet soil also stalls the slips. Wait until after April 3 and until the soil feels warm.
Which frost date matters for sweet potatoes?
The 36F light-frost dates matter most: April 3 in spring and October 31 in fall. The 32F freeze bands (March 12 to March 28 and November 7 to November 20) are wider and later in fall, but tender vines suffer before the air reaches 32F.
How late can I still plant?
It depends on the variety’s days to harvest, counted from setting the slips, and on the October 31 light-frost date at Little Rock. A quick-maturing variety gives you more room than a slow one. If you are unsure, ask your county extension office which varieties finish in time locally.
Do I need to change anything in northern Arkansas?
Yes. Cooler northern counties and higher ground have a shorter season, so plant later in spring, pick faster varieties, and be ready to dig before the first frost. Check the USDA hardiness map and your county extension office for local dates.