Most varieties require at least 4 frost-free months to grow big potatoes. Plants thrive in hot weather.
Start the crop by setting out 6- to 8-week-old slips or draws, available at nurseries in southern states or by the mail, if you are growing your own slips, begin sprouting them about 8 weeks before planting.
Expect about 1 pound of sweet potatoes for each foot of row under average growing conditions.
Add about 3 pounds of 5-10-10 (5 pounds in sandy soils) or its equivalent per 100 feet of row and work it into the soil before planting. Also add fine compost or aged manure to provide a long release of nutrients.
Till the soil to a depth of 8 to 10 inches before planting.
Unless the soil is very sandy, raise the planting bed 6 to 8 inches to make a ridge 1 foot or so wide.
After danger of frost is past and the weather is warm (nights above 55° F), set slips 12 to 18 inches apart along ridges or in rows that are 36 to 48 inches apart. Set the slips in the soil to the depth of the first leaves with several nodes (joints) underground. Firm the soil and make a shallow depression around the plant.
Water beds with a starter solution high in phosphorus. Water beds generously for a few days.
Control weeds by hoeing or mulch the area 4 to 5 weeks after planting.
Side-dress 3 to 4 weeks after transplanting with 3 pounds (5 pounds in sandy soils) of 5-10-10 per 100 feet of row.
Provide deep watering in hot dry periods to increase yields. If planning to store part of the crop, don't give the plants any extra water late in the season.
See our article Summer's Bad Guys by Charlie Nardozzi for controls of common sweet potato pests such as flea beetles.
In most central and southern states harvest sweet potatoes in late September to mid-October, or dig up small potatoes at any time. In the North, harvest before any impending frost.
To harvest, dig roots carefully. Handle storage potatoes carefully, they bruise easily and won't keep well if bumped around. Gently put them in baskets or crates in a warm, humid location for curing.