Sweet potato

Ipomoea batatas · Morning glory family (Convolvulaceae)

At a glance
Hardiness zones	3 to 11
Sun	full sun
Water	moderate
Life cycle	tender perennial (grown as an annual)
Frost	Tender: killed by frost
Soil pH	5.5–6.2
Spacing	12 to 18 inches
Days to harvest	90 to 120 days
Soil temperature to plant	at least 65°F

About Sweet potato

Sweet potatoes are sprawling vines grown from rooted sprouts called slips, and their sweet orange or pale roots store for months. They love heat and need a long, warm frost-free season, which makes them a Southern favorite.

Grown as a summer annual, but it needs a long, hot frost-free season (Texas A&M: about 150 days before soil cools to 55F), so it is easiest in the South and a challenge in short-season northern gardens; it is perennial only in about zones 9-11.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Set out plants: 1 to 2 weeks after the last frost

Days to harvest count from setting out slips; some varieties such as Jewel take 120 to 135 days. Most gardeners buy slips; roots sprouted at home take about 6 weeks to produce them.

Soil

Loose, well-drained sandy loam, ideally on a raised ridge; heavy clay gives small, misshapen roots.

Follow a soil test; without one, till in about 30 lb of 5-10-10 per 1,000 sq ft (about 3 lb per 100 sq ft) or work in compost before setting slips.

Feeding

before the vines cover the row: low-nitrogen fertilizer such as 5-10-10. Spread about 4 lb per 100 ft of row beside the plants and water it in.

Too much nitrogen lowers yield and quality.

Harvest

Dig around the time of the first fall frost, or when about 30 percent of the roots are over 3 1/2 inches across. Cure at about 85F and high humidity for 1 to 2 weeks, then store above 50F.

Dig all at once near season's end, when about 30% of roots are over 3 1/2 inches across, and before frost, since cold soil hurts quality and storage.

Varieties (19)

Variety	Type	Days	Notes
NC Japanese	Asian type, purple skin, white flesh		Purple skin and white flesh.
Centennial	Orange-flesh	100 to 110 days	Moist texture. Smooth skin with deep orange flesh. Resistant to root-knot nematode and wireworms.
Evangeline	Orange-flesh		Light to dark rose skin and intense deep orange flesh. Highly resistant to root-knot nematode and resistant to Fusarium wilt.
Regal	Orange-flesh		Purplish-red skin and dark orange flesh. Resists internal cork, Fusarium wilt, soil rot, root-knot nematode and many soil insects.
Porto Rico	Orange-flesh (heirloom)		Copper to light orange skin with salmon-orange flesh. Susceptible to Fusarium wilt and soil rot.
Vardaman	Orange-flesh, bush type	100 days	Compact bush-type vines. Smooth, oval roots with rich orange flesh; some Fusarium wilt resistance.
Averre	Orange-flesh, early	90 to 100 days	Light rose skin, orange flesh and very high yields in a short season. Resistant to Fusarium wilt.
Beauregard	Orange-flesh, early	90 to 100 days	Light rose skin and moderately deep orange flesh. Resistant to Fusarium wilt and Rhizopus soft rot; very susceptible to root-knot nematode.
Georgia Jet	Orange-flesh, early		Rose skin; high yielding.
Orleans	Orange-flesh, early		Light rose skin like Beauregard with orange flesh; smooth skin that cures and stores well. Resistant to Fusarium wilt; susceptible to root-knot nematode.
Jewel	Orange-flesh, late	120 to 135 days	Copper skin and deep orange flesh. Resistant to Fusarium wilt, southern root-knot nematode and internal cork.
Covington	Orange-flesh, midseason	95 to 115 days	Baked roots rate very good in taste panels, similar to Beauregard. Smooth rose skin and uniform orange flesh with very uniform root shape. Resistant to Fusarium wilt and southern root-knot nematode.
Bayou Belle	Orange-flesh, red skin		Red to purple skin and deep orange flesh; very high yield. Resistant to Fusarium wilt and highly resistant to Rhizopus soft rot.
Burgundy	Orange-flesh, red skin		Red skin with deep orange flesh. Highly resistant to root-knot nematode and resistant to Fusarium wilt.
Carolina Ruby	Orange-flesh, red skin		Deep red skin and orange flesh; high-yielding, blocky roots on thin, trailing vines. Resistant to Fusarium wilt.
Murasaki-29	Purple-skin, white-flesh (Japanese type)	100 to 120 days	Drier, flakier texture with a nutty flavor; less creamy than orange types. Dark purple skin with white flesh on very vigorous vines. Highly resistant to root-knot nematode and resistant to Fusarium wilt.
Sumor	White to yellow flesh	110 to 120 days	Not very sweet; cook it like a white potato. Light tan skin with white to yellow flesh. Resistant to Fusarium wilt, root-knot nematode and many insect pests.
Bonita	White-flesh		Light tan skin with a pink cast and white flesh with a hint of yellow. Highly resistant to root-knot nematode.
O'Henry	White-flesh		Cream skin with white flesh; a white-fleshed mutation of Beauregard.

Good neighbors

Okra

UMD Extension shows sweet potato as a ground cover under okra in an intensive garden; this is a space-saving idea rather than proven pest control.

Pests to watch for

Wireworms, Root-knot nematodes, Cutworms, Whiteflies, Mole crickets, Roof rats and Norway rats, Red imported fire ant, Beet armyworm, Sweetpotato weevil, Voles

Diseases and problems

Black rot, Fusarium wilt, Scurf, Internal cork, Streptomyces soil rot, Frost and freeze injury, Southern blight, Sooty mold

In the kitchen

Baked, roasted, mashed or made into pies and fries; orange-fleshed types are especially sweet.

Keeping it: After curing, keep sweet potatoes at 55 to 60F with moderate humidity for 4 to 6 months. Don't refrigerate raw roots; cold below 55F causes off-flavors and dark spots.

Pets: Listed as non-toxic to dogs, cats and horses (ASPCA, 'Sweet Potato Vine').

Sources

Photo: Photo: Llez, CC BY-SA 3.0, via Wikimedia Commons (CC BY-SA 3.0). Photo resized for the web.

Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.