Sweet potatoes are tender, warm-season perennial plants grown as annuals.
Sweet Potato Quick Growing Tips
- Sweet potatoes require a long, warm growing season, usually about 4 months of frost-free weather to reach harvest.
- Set sweet potato starts or slips in the garden after all danger of frost has passed, usually 4 weeks after the last average frost date in early summer.
- Sweet potatoes grow best where the air temperature remains very warm, from 75° to 95°F (24-35°C) throughout the growing season.
- Sweet potatoes are best started indoors as early as 12 weeks before they are placed in the garden.
- Sweet potatoes require from 100 to 150 days to reach harvest.
Where to Plant Sweet Potatoes
- Plant sweet potatoes in full sun.
- Grow sweet potatoes in loose, well-worked, well-drained loamy or somewhat sandy soil with aged compost added.
- Prepare the planting bed by adding aged compost and aged manure or a commercial organic planting mix across the bed then turn the soil 12 inches (30cm) deep.
- Soil that is overly rich in nitrogen will produce more foliage than tubers.
- Remove all soil lumps, rocks, or other obstacles from the planting bed; if tubers hit an obstacle as they develop, they will grow deformed.
- Sweet potatoes prefer a soil pH of 5.0 to 6.5.
Sweet Potato Planting Time
- Set sweet potato starts in the garden after all danger of frost is past in spring, usually about 4 weeks after the last frost.
- Sweet potatoes are extremely sensitive to frost and need a warm, moist growing season of as many as 150 days.
- Sweet potato slips can be started indoors as early as 12 weeks before they are transplanted into the garden.
- Well-rooted sweet potatoes require a soil growing temperature of 60° to 85°F (16-29°C) and an air growing temperature of 65° to 95°F (18-35°C).
- Sweet potatoes will thrive in air temperatures as high as 100°F (37°C).
Starting Sweet Potato Sprouts or Slips Indoors
Grow sweet potatoes from rooted sprouts, called slips, taken from a mature tuber. Here are two ways to start sweet potato slips:
- Place the sweet potato in a jar of water that is half full with about one-third of the tuber submerged. Leave it in a warm (75°F/24°C)), sunny location where it will sprout. When sprouts are 6 inches (15cm) long, pull them off the tuber and set them in water or damp sand; they will root in a few days. Start this process about 12 weeks before you plan to set the slips in the garden.
- Place cut pieces of a tuber moist sand or light growing medium with a constant temperature of about 80°F (26°C). (Use a heating mat with a thermostat to keep the soil consistently warm.) Each piece must have one or more “eyes or sprouts. Set each piece 2 to 4 inches (5-10cm) deep in sand or light soil. Shoots will appear in about 3 weeks. When shoots appear, add another inch of sand or light soil. Do not let the growing medium dry out. When sprouts reach 3 to 4 inches (7-10cm) tall reduce the soil temperature to 70°F (21°C) and grow on for another 3 weeks. Seed tubers will be rooted in about 6 weeks and can then be planted in the garden.
You can start slips in one-gallon containers or in a hotbed. If you plant in a hotbed space slips 3 to 4 inches (7-10cm) apart.
One sweet potato tuber can yield as many as a dozen slips.
Planting Sweet Potatoes in the Garden
- Set rooted slips in the garden on mounded rows 12 inches (30cm) wide and 8 inches (20cm) high; space rows 3 feet apart (.9m); plant slips at 12 to 18-inch (30-45cm) intervals.
- Plant slips so that the sprouts grow up toward the sky, not sideways. Be sure to cover all of the roots and about a ½ inch (12mm)of the stem.
- Protect tender sweet potato foliage from the direct hot sun for five days after planting. Set a floating row cover over the plants.
- Grow 5 sweet potato plants for each household member.
Companion Plants for Sweet Potatoes
- Grow sweet potatoes with other root crops: beets, parsnips, and salsify.
Container Growing Sweet Potatoes
- Grow a single sweet potato plant in a box or tub that is at least 12 inches (30cm) deep and 15 inches (38cm) wide.
- Use a light, porous soil mix.
- Place a stake or trellis in the center to support the vine which grows up and outwards.
Watering Sweet Potatoes
- Sweet potatoes will tolerate dry soil once established but will produce best if kept evenly moist, an inch of water every week (1 inch equals 16 gallons/60.5 liters) until 3 to 4 weeks before harvest.
- Do not overwater sweet potatoes; tubers will rot in soil that is too wet.
Feeding Sweet Potatoes
- Add aged compost or commercial organic planting mix to planting beds before planting. Aged compost contains all the nutrients sweet potatoes need to get started.
- Feed newly planted slips with a B-1 starter solution or compost tea.
- Add a low nitrogen fertilizer (5-10-10) to the soil two weeks before planting.
Maintaining Sweet Potatoes
- Sweet potatoes are easily trained onto trellises, lattices, or wires strung between sturdy poles.
- Keep weeds away from young plants. Mulch around plants with loose straw or chopped, dried leaves to control weeds and slow soil moisture evaporation.
- Pull weeds by hand or cultivate shallowly to avoid disturbing roots. Eventually, the foliage of the maturing sweet potato plant will shade out new weeds.
Sweet Potato Pests
- Insects are not likely to attack sweet potatoes in northern regions. In southern regions, sweet potato weevils and wireworms are common pests.
- Weevil larvae chew holes in tubers and adults chew holes in leaves. Control adult weevils by knocking them from plants and crushing them or spray with pyrethrins.
- Plant resistant varieties.
- Where heavy infestations occur remove all plants and do not re-plant in that area for three years.
Sweet Potato Diseases
- Sweet potatoes are susceptible to root rot and fungal diseases including a fungus disease called scurf.
- Plant disease-resistant varieties and keep the garden clean of debris and weeds where pests and diseases can harbor.
- Remove and destroy infected plants immediately before the disease can spread to healthy plants.
- Scurf is a fungal disease that grows on the skin of sweet potatoes. The skin develops shallow purple or grayish-brown lesions. Prevention is the best control. Plant certified disease-free slips. Rotate sweet potatoes out of an infected bed for three years.
Harvesting Sweet Potatoes
- Sweet potatoes require from 100 to 150 days to reach harvest.
- Lift sweet potato tubers when they have reached full size, commonly when leaves and vines have begun to yellow and wither.
- Carefully dig plants using a garden fork starting about 15 to 18 inches (38-45cm) from the center of the vine and working inwards lifting. Tubers will be 6 inches (15cm) or so deep in the soil. Be careful not to cut or bruise the tubers which are thin-skinned.
- Complete the harvest before the first frost in fall; tubers are damaged by freezing or cold weather.
Storing and Preserving Sweet Potatoes
- Cure (dry and harden) sweet potato tubers for 10 to 15 days after harvest. Set them in a warm spot (about 80°F) out of direct sunlight. Curing will help heal nicks and cuts and harden the skin. Curing will also improve the sweetness of the tuber.
- Sweet potatoes will store at 55° to 60°F (13-16°C) in a dry, cool, well-ventilated place for 4 to 6 months.
- Store sweet potatoes unwashed. Wrap the tubers in a newspaper when you store them; don’t let the tubers touch or they may rot.
- Do not refrigerate or store sweet potatoes at temperatures below 50°F (10°C).
- Sweet potatoes can be frozen, canned, or dried.
Sweet Potato Varieties to Grow
- Sweet potato tubers are described as “dry” and “moist” noting the texture of the tuber when eaten. “Moist” sweet potatoes are often called yams; however, the true yam is actually a different species found in tropical regions.
- Varieties: ‘Beauregard’ (moist-fleshed, 100 days); ‘Boniato’ (dry-fleshed, 120 days); ‘Centennial’ (moist-fleshed, 110 days); ‘Georgia Jet’ (moist-fleshed, 100 days); ‘Goldrush’ (140 days); ‘Jasper’ (150 days); ‘Jewel’ (moist-fleshed, 100 days); ‘Nancy Hall’ (moist-fleshed, 110 days); ‘Porto Rico’ (moist-fleshed, 110 days); ‘Southern Delite’ (moist-fleshed, 100 days); ‘Vardaman’ (moist-fleshed, 110 days); ‘White Yam’ (dry-fleshed, 120 days); ‘Yellow Jersey’ (dry-fleshed, 120 days).
About Sweet Potatoes
- The sweet potato is a tender vining or semi-erect perennial plant grown for its swollen fleshy tuber, similar to an elongated potato.
- Tubers grow underground from the vine’s central shoot.
- Tubers vary from creamy-yellow to light brown to deep red-orange in color and from 4 or 5 inches (10-12cm) to 8 inches (20cm) or more in length.
- The flesh of the tuber is yellow or gold.
- The flower of the sweet potato is pink to purple colored.
- Botanical name: Ipomoea batatas
- Origin: Tropical America and the Caribbean
More tips: How to Harvest and Store Sweet Potatoes