How to Plant and Grow Sweet Potatoes

Sweet potatoes are tropical plants related to morning glories and are very easy to grow. They do require a long, warm growing season to mature, which is why they've long been a Southern favorite. However, newer, faster maturing varieties make it possible to grow sweet potatoes in northern gardens that have a shorter growing season. And while traditional varieties of sweet potatoes command a good bit of garden space—their vines often cover several feet of ground—there are bush varieties that are better suited to smaller gardens. Here's how to plant and grow sweet potatoes in your garden.

Where to Plant Sweet Potatoes

Choose a spot in full sun to plant sweet potatoes. They will grow in less than full sun but will not produce as well. Your planting site should also be well-drained or your sweet potato roots may rot. If your soil is poorly drained or rocky, grow your sweet potatoes in raised beds or large containers. These plants often spread widely, so be sure you have adequate planting space.

How and When to Plant Sweet Potatoes

Sweet potatoes are very sensitive to cold so wait to plant slips (sprouts) of sweet potatoes until spring weather has warmed and all danger of frost has passed. Make sure the soil has warmed to about 65°F, usually about three to four weeks after the last frost. Space slips 12 to 18 inches apart in rows that are 3 to 4 feet apart.

In cool-summer areas, you can plant the slips through slits in sheets of black plastic mulch, which will warm the soil and speed development. If you experience some cool night temperatures, cover newly planted slips overnight with a plastic pot or row cover to protect your plants from a cold snap.

Sweet Potato Care Tips

Light

The more sunlight that you have for growing sweet potatoes, the better. A minimum of 6 hours direct sun per day is best.

Soil and Water

Although sweet potatoes grow best in a sandy soil, any well drained garden soil with a pH of 5.8 to 6.2 is fine. To improve drainage, enrich soil with organic matter to a depth of 8 to 10 inches.

Water newly planted slips regularly until they are established, then provide about an inch of water per week to your sweet potato patch. Reduce watering 2 to 3 weeks before harvest to reduce cracking of the sweet potato skin, which can cause problems in storage.

Temperature and Humidity

Sweet potatoes love hot weather and grow best where temperatures range between 65-95°F. They thrive in areas with high humidity, but they will tolerate average humidity, too.

Fertilizer

The best time to add fertilizer is just before planting. Because sweet potatoes are not heavy feeders, working compost into the soil at planting time usually provides sufficient nutrients. A slow-release organic fertilizer can also be added to the soil prior to planting. Do not over-fertilize, especially with nitrogen, as this will lead to excess leafy growth at the expense of production of the sweet potato roots.

Pruning

Don't prune the sweet potato vines—the leaves are necessary to manufacture the food that is stored in the tuberous roots. If your vines wander further than you want them to, just lift them up and direct them to grow elsewhere.

Pests and Problems

Deer are fond of sweet potato leaves and can decimate a planting. If deer are a problem in your yard, protect the plants with fencing or netting. Few other pests cause significant problems although golden tortoise beetles, aphids, and a variety of caterpillars sometimes feed on the leaves. In some areas, wire worms and root knot nematodes can cause problems underground. 

Fusarium wilt and black scurf are fungal diseases that may infect sweet potatoes. Fusarium wilt causes leaves to turn yellow and vines to wilt. Sweet potatoes infected with black scurf develop rounded black blotches on the sweet potato. The best prevention for diseases is to plant certified disease-free slips, choose resistant varieties, and rotate your sweet potato patch each year.

How to Propagate Sweet Potatoes

Unlike the regular potato, which is a tuber (a modified stem), the sweet potato is a tuberous root. This difference is significant in how new plants are started. To plant potatoes, you simply cut a potato into pieces, each with a couple eyes, and plant it. Sweet potatoes are planted from slips, which are rooted stems that grow from the sprouting end of a sweet potato. Growing slips is not difficult, but it does take some time; you can also purchase slips either by mail order or from your local garden center.

To grow your own sweet potato slips, purchase a healthy, untreated sweet potato and set it lengthwise in a container of potting soil or sand and cover the lower half of the sweet potato with potting soil. Keep it moist and warm. Within a few weeks, shoots will begin to sprout from one end. When the shoots reach about six inches long, break them off the sweet potato and place the lower end of the slip in water where it will form roots. One sweet potato will usually produce 10 to 20 slips. If you have a long warm season, you can take stem cuttings off growing plants and place the cuttings in water to root for a second planting.

Harvesting and Storing Sweet Potatoes

Harvest your sweet potatoes in the fall when weather begins to turn cooler and vines start with wither. Aim to harvest before your area's first frost—a light frost won’t usually damage the roots, but a hard frost may injure roots near the soil surface.

Use a garden fork to lift the sweet potatoes and brush soil from the roots. Damaged roots should be separated for immediate use. Undamaged roots can be cured for storage by placing them in a warm room (80 to 90°F) ideally with high humidity for five or six days. Curing heals small scratches and starts the conversion of starches to sugars, which improves flavor. If kept in a dark space where temperatures stay between 50 and 60°F, cured sweet potatoes can be stored for several months.

Types of Sweet Potatoes

‘Beauregard’ is an old favorite with reddish skin and deep orange, moist, sweet flesh. It is a heavy producer, disease resistant, and matures in 100 days.

‘Georgia Jet’ is a good choice for gardeners in cooler regions. It tolerates cooler temperatures than most varieties and matures in about 90 days. Its flesh is bright orange and has excellent flavor.

‘Bush Porto Rico’ produces heavy yields on more compact plants, so is well suited to smaller gardens. Its flesh is reddish-orange, and it matures in 110 days.

‘O’Henry’ is a tan skinned variety with creamy-yellow, somewhat dry flesh with a delicate flavor. It produces good yields of very large (sometimes cantaloup sized) sweet potatoes in about 100 days.

‘Murasaki’ is a popular Japanese variety with purple skin and dry, cream-colored flesh that has a rich, nutty flavor. It takes 105 to 120 days to mature.