Harvest guide
When to Plant Sweet Potatoes (Soil Temp + Frost Timing)
Plant sweet potato slips 2 to 4 weeks after your last spring frost, once soil holds above 65°F. Get timing by zone, the soil-temp gate, and the mistake that rots slips in cold ground.
Days to maturity
90–120days
Ready when
Before first frost; dig when leaves yellow
The short answer
Plant sweet potato slips 2 to 4 weeks after your last spring frost, once the soil holds steady above 65°F at planting depth. In most US zones that lands in May or early June. They are a warm-season crop with no frost tolerance, so warm soil matters more than the calendar date.
Sweet potatoes are planted from rooted cuttings called slips, not from seed potatoes. You set the slips out once, in late spring, and dig the roots in fall. Timing is the whole game. Plant too early into cold soil and the slips sit, sulk, or rot. This guide covers when to plant by zone, the soil-temperature check that beats any calendar date, and the early-planting mistake that costs a row.
Soil temperature is the real green light
The date on the calendar matters less than the temperature in the ground. Sweet potatoes are a tropical crop, and cold soil shuts them down.
Clemson Extension lists 65°F as the floor for transplanting slips, and says to plant well after the last chance of frost. NC State Extension frames it by weather rather than a fixed date: the crop wants warm conditions with nights in the upper 60s or 70s.
So the rule that works in every zone: wait until soil at planting depth holds above 65°F and night temperatures have settled. A cheap soil thermometer pushed 4 inches into the bed settles the question in a minute.
Pro tip
Slips are frost-tender and chill-sensitive, so the air matters too, not just the soil. Hold off until nighttime lows stay reliably above the low 60s°F. A warm afternoon followed by a 45°F night still stresses a fresh transplant. If a late cold snap threatens after planting, cover the row with fabric or a light sheet overnight.
When to plant by zone
The soil-temp rule translates into different calendar windows by region, because warm ground arrives at different times. The windows below are starting points, not deadlines.
The target is the same everywhere: 2 to 4 weeks after your last spring frost, once soil is above 65°F. Warmer zones hit that mark in April, colder zones not until late May or June.
| Region / zone | Typical planting window | The cue |
|---|---|---|
| Deep South / Gulf (zones 8–9) | Mid-April – May | Soil above 65°F, frost long past |
| Mid-South (zones 7–8) | Early – late May | 2 to 4 weeks after last frost |
| Mid-Atlantic / Midwest (zones 5–7) | Mid-May – early June | Soil holds 65°F, nights in the 60s |
| Far North (zones 3–5) | Late May – June | Warm a bed first, use an early variety |
University of Maryland Extension puts mid-Atlantic planting in this same late-spring window, once frost danger is gone and soil has warmed. Shift earlier as you go south, later as you go north.
How to tell it is time to plant
You do not need to guess. Three signals together mean go.
- Your last spring frost date has passed by at least 2 weeks.
- Soil at 4 inches deep reads above 65°F for several days running.
- Nighttime lows stay above the low 60s°F, not just daytime highs.
If all three are true, set your slips. If soil is still cool, wait. A row planted into 60°F soil a week early gains nothing and risks rot.
Growing in a short season
Sweet potatoes can grow well north of their comfort zone, but the cold-soil problem gets sharper. Northern gardeners have to manufacture the warmth.
Most varieties need 90 to 120 days from transplant to harvest, and the vines die at the first frost, so a short-season garden has no margin to waste. Three moves close the gap:
- Warm the soil with black plastic mulch laid a week or two before planting. NC State and other extensions recommend it to raise soil temperature and speed early growth in cooler climates.
- Choose an early-maturing variety, which finishes inside a 90-to-100-day frost-free window.
- Count back from your first fall frost. Subtract the variety's days to maturity, then plant once soil passes 65°F, whichever is later.
Common mistake
The costly error is planting too early into cold soil. Sweet potatoes have no frost tolerance and stall below about 65°F. Slips set into cold, wet ground before it warms will sit still, rot at the base, or grow weakly all season. Beating your neighbor by two weeks means nothing if the row fails. Wait for warm soil, even if the calendar says you are late. A late start in warm ground outruns an early start in cold ground every time.
Why there is no fall planting
Sweet potatoes are planted once, in late spring or early summer, for a fall harvest. They are not a fall-planted crop like garlic.
The roots size up through the heat of summer and finish in early fall. Because the vines are killed by frost, you dig before the first fall frost, not plant into it. In warm climates a grower can plant late into summer with a short-season variety, but that is still a warm-season planting reaching for a fall harvest, not a cool-season one.
So plan one planting, in warm soil, and one harvest, before the cold returns. The payoff is covered in when to harvest sweet potatoes, which walks the dig-before-frost timing and the curing step that makes them sweet.
Space the slips while you plant
Spacing is set at planting, so get it right the day the slips go in. Sweet potatoes are vigorous and need room for the roots to bulk up.
Lay the bed out before you plant so each slip has its share of ground. The how far apart to plant sweet potatoes guide gives the in-row and between-row numbers, and the plant spacing calculator counts how many slips fit your exact bed.
Sweet potatoes share the warm-soil rule with the rest of the summer garden, even though they are a different crop from their namesake. The cool-season cousin runs on the opposite clock, which is why when to plant potatoes lands weeks earlier in spring.
Your next step
If you take one thing from this page: ignore the calendar and check the ground. Push a soil thermometer 4 inches into the bed, and once it reads above 65°F for a few days with warm nights, set your slips, 2 to 4 weeks past your last frost.
Ready to lay out the row? Open the plant spacing calculator and set sweet potatoes so every slip has room to size up.
Common questions
What month is best to plant sweet potatoes?
It depends on your last frost date, not the calendar. Most US gardeners plant slips in May or early June, 2 to 4 weeks after the last spring frost, once soil holds above 65°F. The Deep South and the Gulf can plant from mid to late April. Far-northern gardens wait until late May or June.
What soil temperature do sweet potatoes need to be planted?
Wait until soil stays above 65°F at planting depth. Clemson Extension lists 65°F as the floor for transplanting slips, and NC State notes the crop wants warm weather with nights in the upper 60s or 70s. Cold soil stalls or rots the slips, so warm it before you plant.
Can you plant sweet potatoes too early?
Yes, and it is the most common mistake. Sweet potatoes are a warm-season crop with no frost tolerance. Slips set into cold, wet soil before it warms to 65°F sit still, rot, or grow poorly. Waiting two extra weeks for warm soil beats replanting a row that failed.
How long do sweet potatoes take to grow after planting?
Most varieties need 90 to 120 days from transplanting slips to harvest, per University of Maryland Extension and the common extension range. Short-season gardeners should pick an early variety and count back from the first fall frost, since the vines are killed by frost.
Can I plant sweet potatoes in fall?
No. Sweet potatoes are planted once, in late spring or early summer, for a fall harvest. They are not a fall-planted crop. In warm climates you can plant late into summer with a short-season variety, but that is still a warm-season planting, not a cool-season one.
Sources
Agronomic claims in this guide are checked against these primary sources.
- Sweet Potato — Clemson Cooperative Extension
- Sweet Potatoes — University of Maryland Extension
- Growing Sweetpotatoes in North Carolina — NC State Extension
Keep reading
When to Harvest Sweet Potatoes (Signs They're Ready)
Sweet potatoes are ready about 90 to 120 days after transplanting, before the first fall frost. Dig when the vines yellow, then cure before you eat them.
Read →When to Plant Potatoes (Timing by Zone + Soil Temp)
Plant potatoes about 2 to 4 weeks before your last spring frost, once the soil warms to 45 F. That falls February to April in most US zones. In the South, a second crop goes in late summer for a fall dig.
Read →When to Plant Zucchini (Frost + Soil Temp Timing)
Plant zucchini after your last spring frost, once the soil hits at least 60 F (ideally 65 to 70 F). Direct-sow seeds 1/2 to 1 inch deep, or set out transplants started 2 to 4 weeks earlier. Warm zones get a second fall crop.
Read →When to Plant Tomatoes (Frost + Soil Temp by Zone)
Set tomato transplants out 1 to 2 weeks after your last spring frost, once soil hits at least 60 F. Start seeds indoors 6 to 8 weeks before that frost date. Cold soil stalls them, so wait for warmth.
Read →When to Plant Swiss Chard (Spring and Fall Timing)
Plant swiss chard 2 to 4 weeks before your last spring frost, once the soil hits 40°F. Sow again 3 to 4 weeks before the first fall frost. Seeds go half an inch to an inch deep.
Read →When to Plant Spinach (Spring and Fall Timing)
Plant spinach 4 to 8 weeks before the last spring frost, as soon as the soil hits 40°F. Sow a fall crop 6 to 8 weeks before the first fall frost. Seeds go in 1/2 inch deep, direct-sown.
Read →