By Marion Barnes, Senior County Extension Agent
The South Carolina Lowcountry is a great place to grow sweet potatoes (Ipomea batatas) in the home garden due to our long growing season and well drained soil types. Sweet potatoes are highly nutritious and a great source of fiber, vitamins, minerals and complex carbohydrates. They are a healthy alternative to white potatoes, which have a high glycemic index. Sweet potatoes are in the morning glory plant family (Convolvulacea) and produce enlarged, edible storage roots. This tropical, warm season plant is a Native American crop and originated from South America.
The following are a few tips for anyone considering planting sweet potatoes in the home gardens.
Optimum planting dates for sweet potatoes in the Coastal region of the state are generally April 15 through July 1. Be mindful of late frost that may occur in April to avoid freeze damage.
Sweet potatoes plants require full sun to develop fully and need to receive 8 to 10 hours of sun each day. Due to their long trailing vines, avoid planting them near garden plants with upright growth habits. Taller plants such as sweet corn can block out sunlight to lower growing sweet potato vines.
Soil type and fertilization
Sandy, or well-drained loamy soils are best for growing sweet potato. Compacted soils can negatively impact storage root shape and development. Poorly drained and high clay content soils can result in lower yields and rotted storage roots. Sweet potatoes are tolerant of wide of soil pH ranges, but do best at 6.0 to 6.5 soil pH. Proper fertilization begins with a soil test. Base fertilization on soil test results.
Soil preparation, planting and watering
Soil temperatures should be above 65 degrees F. before planting. Sweet potatoes are grown from transplants called “slips”, which are produced from roots of the previous season’s crop. Most gardeners choose to purchase slips from garden stores since sweet potatoes for seed are difficult to obtain and start. Plant slips on raised beds, 3 feet apart to allow for early cultivation and weed control and 8 to 12 inched apart on the row. Water is especially important during the transplant, establishment, and root development stages. Sweet potatoes require at least 1 inch of water (rainfall or irrigation per week) for normal growth. Always water plants in the morning to reduce incidence of disease. Excessive watering during the latter stages of storage root development can lead to splitting.
Weeds, diseases and insects
Weed control is most challenging and important until plants cover the row. Shallow cultivation is necessary to prevent root damage. Several insects and diseases can damage sweet potatoes. Soil borne insects like wireworms and nematodes are the most common. The guava root-knot nematode considered one of the most damaging in the world because of its wide host range was identified in commercial sweet potatoes in Darlington County in 2017. The guava root-knot nematode can affect other vegetables like peppers, cucumbers, watermelons and tomatoes crops. The sweet potato weevil is another serious pest, especially to commercial growers and is found in several counties along the coast. Purchasing certified, disease free, resistant varieties can help reduce the spread of destructive pests.
Harvest, curing and storage
Most sweet potatoes varieties should be ready for harvesting about 90 to 120 days after planting. Harvest before frosts cool soil temperatures, which can reduce yield, quality and storage life. Sweet potato skin is extremely thin, so care should be taken not to bruise, or damage freshly dug roots when digging and handling. For proper curing, air dry sweet potatoes out of direct sun light at temperatures of 80-85 degrees Fahrenheit. Store where temperature do not fall below 55 degrees Fahrenheit and check for decay or rot frequently. Under good conditions, sweet potatoes can be stored for six or more months.
Sweet potatoes are a versatile southern food and can be prepared and enjoyed in a variety of ways. If you chose not to grow your own sweet potatoes, there is always the option of visiting your local farmers market in the fall and purchasing them fresh from our local farmers.
For more information on growing sweet potatoes check out the Clemson Extension Home and Garden Factsheet HGIC 1322, Sweet Potato at: https://hgic.clemson.edu/factsheet/sweet-potato/