Transplant outside
2–3 weeks after last frost
Raised beds or deep in-ground beds preferred; containers work but limit yield significantly. In containers: 15-gallon pot, at least 12 inches deep. Space plants 12 inches (30 cm) apart.
Crop guide · The morning glory family
How to grow sweet potatoes
A warm-season root crop that produces generous harvests of sweet, starchy tubers from slips planted after the soil has fully warmed.
Ipomoea batatas · also called yam (common misnomer), camote
Full sun
Intermediate
Frost-tender
Sun
Full sun
Vines tolerate heat well
Frost
Tender
Vines blacken at the first light frost
Spacing
12 in
30 cm between plants
Sow depth
4 in
102 mm
To harvest
90–120 days
counted from transplant
Soil pH
5.5–6.5
on the acidic side
Timing
When to plant sweet potatoes
Windows are counted from the average date of your last spring frost.
Last frost
Transplant outside
2–3 weeks after
2–3 weeks after last frost, once soil reaches 65 °F (18 °C) or above.
First harvest
14–21 weeks after
90–120 days counted from transplant, so first pickings start around 14 weeks after the last frost.
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Weeks relative to last spring frost
Summer:up to 16 weeks before first fall frost in warm climates.
Too late?Skip planting if fewer than 90 frost-free days remain — tubers need the full season to size up before cold arrives.
Background
Why grow sweet potatoes
Home-grown sweet potatoes cure to a richer sweetness than store-bought, and the vines double as ornamental ground cover. A single 10-foot row can yield 10–20 pounds of tubers with minimal pest pressure.
A little history. Native to tropical America; archaeological evidence places cultivation in Peru as far back as 8,000 years ago. Unlike the true yam (family Dioscoreaceae), sweet potato belongs to the morning glory family and is not closely related.
The season, step by step
From planting to harvest
Water and feed
All season
Water deeply once or twice a week during vine establishment; reduce to once a week once vines cover the ground. Water when the top 2 inches of soil feel dry, or vines show slight midday wilting. Aim for about 1 inch per week including rain.
Apply at planting, then side-dress (scatter fertilizer along the row and water in) once at 4 weeks; stop feeding by midsummer. What to use: low-nitrogen, higher-phosphorus and potassium fertilizer (e.g. 5–10-10 organic); excess nitrogen drives vines at the expense of tubers.
Prune and maintain
As it grows
Lift vines off the soil every 2–3 weeks to prevent them from rooting at nodes and diverting energy from the main tubers. Do not remove vines entirely.
Harvest and store
90–120 days from transplant
It's ready when skin resists scratching with a fingernail and tubers are 2–3 inches in diameter. Harvest before the first frost; vines yellowing naturally also signals maturity. Loosen soil 12 inches from the crown with a fork, then lift carefully — tubers bruise easily. Cut vines back to 6 inches first. Work on a dry day to reduce soil adhesion.
Cure unwashed tubers at 85–90 °F (29–32 °C) with high humidity for 5–7 days to harden skin, then store at 55–60 °F (13–16 °C) in a dark, ventilated space for up to 6 months. Never refrigerate.
Companions
Good neighbours, bad neighbours
Plant it with
Thyme
A low band of strongly scented thyme along the bed edge can help hide sweet potato foliage from pests that hunt by smell, and it stays short enough that the running vines simply grow over and past it.
Oregano
Let a plant or two of oregano flower at the bed edge; the small blooms feed hoverflies, lacewings, and tiny parasitic wasps that often reduce whitefly numbers on nearby sweet potato vines.
French Marigold
French marigold has been shown to reduce root-knot nematodes, which scar and deform sweet potato tubers — but only when grown thickly as a solid stand and turned into the soil at season's end, not as a few edge flowers.
Pole Bean
Pole beans bank nitrogen in their roots, most of which is released for the following season as those roots break down. Trellis them on the north edge so they do not shade the sprawling sweet potato vines.
Keep it away from
Tomato
Both crops are good hosts for root-knot nematodes, so pairing them in the same bed can build populations that scar sweet potato tubers and stunt tomato roots. Keep them in separate beds where nematodes are known.
Zucchini
Two ground-covering crops in one bed means a tangle: broad zucchini leaves shade out sweet potato vines, and stepping in to cut fruit compacts the loose soil the tubers need to swell.
Okra
Sweet potato vines run hard and often blanket the base of young okra, competing for water and light. Both crops also feed root-knot nematodes, so pairing them can build up soil populations that stunt the following season.
Crop rotation
After this crop
Family rest
Easy-going — Sweet Potato can grow almost anywhere in the rotation without a strict rest.
Good next crops
The pea and bean family, the cabbage family or the tomato family thrive in this ground next season.
Sweet potato is a light feeder that leaves loose, well-worked soil but little organic matter behind. Give the bed a year before sweet potatoes or morning glory relatives return, longer if scurf or wilt appeared. Beans, cabbage-family greens, or tomatoes and peppers follow well.
Trouble to watch for
Pests and diseases
Pests
Sweet potato weevil
Sign
Tiny blue-black beetles on vines; tunneling damage and frass inside tubers at harvest.
Fix
Destroy infested plant material immediately; use certified weevil-free slips and rotate beds annually.
Wireworm
Sign
Narrow tunnels bored into tubers, visible at harvest; plants may wilt if larvae attack roots.
Fix
Avoid planting in beds that followed sod or grass; harvest promptly and do not leave tubers in the ground after vines die.
Whitefly
Sign
Clouds of tiny white insects rising from disturbed foliage; sticky honeydew on leaves.
Fix
Spray undersides of leaves with insecticidal soap; remove heavily infested leaves.
Deer and voles
Sign
Ragged vine tips browsed off; tubers with gnaw marks or missing sections at harvest.
Fix
Use wire mesh barriers around the bed perimeter; harvest as soon as tubers reach size.
Diseases
Black rot
Sign
Dark, sunken circular lesions on tubers; infected flesh turns black and bitter.
Prevent
Use certified disease-free slips; cure harvested tubers promptly at 85–90F for 5–7 days to seal wounds.
Fusarium wilt
Sign
Yellowing and wilting of vines from the base up; dark discoloration inside the stem when cut.
Prevent
Plant resistant varieties; avoid replanting sweet potatoes in the same bed for at least 3 years.
Scurf (soil-borne surface mold)
Sign
Brown to black irregular patches on the tuber skin; flesh beneath is unaffected.
Prevent
Rotate beds; improve drainage; use clean slips from a reputable source.
FAQ
Common questions about sweet potatoes
When should I plant sweet potatoes?
Spring: 2–3 weeks after last frost, once soil reaches 65 °F (18 °C) or above. Summer: up to 16 weeks before first fall frost in warm climates.
How long until sweet potatoes are ready to harvest?
90–120 days, counted from transplant. It's ready when skin resists scratching with a fingernail and tubers are 2–3 inches in diameter. Harvest before the first frost; vines yellowing naturally also signals maturity.
Can I grow sweet potatoes in a container?
Raised beds or deep in-ground beds preferred; containers work but limit yield significantly. In containers: 15-gallon pot, at least 12 inches deep.
How often should I water sweet potatoes?
Water deeply once or twice a week during vine establishment; reduce to once a week once vines cover the ground. Water when the top 2 inches of soil feel dry, or vines show slight midday wilting.
How should I store sweet potatoes after harvest?
Cure unwashed tubers at 85–90 °F (29–32 °C) with high humidity for 5–7 days to harden skin, then store at 55–60 °F (13–16 °C) in a dark, ventilated space for up to 6 months. Never refrigerate.
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