How to Grow Sweet Potatoes
A tip sheet on how to grow and care for sweet potatoes.
Sweet Potato (Ipomea batatas)
- Family: Convolvulaceae (Morning-glory)
- Season: Warm
- Ease of growing: Easy
- Nutrient needs: High
- Water needs: Low-medium
- Common propagation: Slips
- Weeks to grow slips: 8 to 12
- Start: March
- Plant out: late May to June
- Typical pacing: 12” in 36” rows
- Plants per square foot: 0.5
- Time to harvest: 100 to 160 days
The edible portion of a sweet potato plant is its root (not a tuber like the Irish potato). The most commonly grown varieties have a moist, soft and sweet flesh that varies from nearly white to a dark orange. The darker varieties are sometimes called yams. The “true” yam, however, is an entirely different plant (Dioscorea alata) that is native to tropical areas. “Beauregard” is the most commonly grown variety in Michigan, due to its rapid maturity and good performance under cooler conditions. However, other varieties like Centennial and Covington have also been reported to do well in Michigan.
Preparation and planting
The sweet potato plant is a spreading vine that performs best on lighter textured soils. Sweet potatoes are usually started from young plants, called “slips,” that are grown from the root. Slips can usually be purchased from garden centers or seed catalogs. To start them at home, suspend a healthy root – pointed end up – with toothpicks in a glass of water. In a few weeks, new plants should start to grow, although some store-bought roots may have been treated with sprout inhibitors. When 3 inches or more, these slips can either be planted directly in the field, or planted in a pot to produce a transplant for field planting. Soils should be at least 65°F.
Provide frost protection if you plant early. When the plants are established, they need very little water because of their deep rooting. Go easy on the nitrogen fertilizer as too much will produce beautiful vines but few roots.
Insects: Flea beetles and wireworms
Diseases: Black rot, Fusarium stem rot, scurf
Harvesting and storage
Harvest tubers when they reach 5 to 6 inches in length and about 2 inches in diameter as these are the best quality. Complete the harvest before a killing frost. Tubers on dead vines tend to rot. Dig them just like potatoes, taking care not to bruise or damage their skins. If the weather is dry, let them sit on the ground for several hours before bringing them in. To cure for storage, provide warmth (80°F to 90°F) and high humidity for 5 to 10 days. Once cured, sweet potatoes should be stored at about 60°F and high humidity. Under these conditions, some varieties can be stored for up to a year.
Developed by James Manning, Undergraduate Research Assistant, and Daniel Brainard, Vegetable Extension Specialist; MSU Department of Horticulture; Gary Heilig, MSU Extension educator.