Don’t confuse your sweet potatoes and yams! Sweet potatoes are mostly cultivated for their smooth-skinned, edible, starchy roots and can be found in colors ranging from white, pink, or violet to yellow or orange. Not a “potato” at all, these plants are part of the morning glory family, and vines will grow well as a groundcover or a houseplant. Native to tropical areas of Central and South America where it was domesticated at least 7,000 years ago, plants prefer a warm climate and will not tolerate frost. Leaves are green or purple and usually heart-shaped or lobed. This easy-to-grow plant will provide you with a tasty harvest each year.
The Covington sweet potato was bred at North Carolina State University in the mid 2000s and has slowly started to take over the sweet potato industry, even surpassing the Beauregard variety’s number one spot in terms of commercial production. The Covington is highly valued for its uniform shape and size as well as long shelf life. The skin of this potato is purplish-red in color and has tender, orange flesh.
Seed: Sweet potatoes are not often grown from seed.
VEGETATIVE: Commonly propagated by planting slips, which are new shoots grown from last season’s roots. To collect your own slips, cut a sweet potato in half and place in a small bowl that’s filled with water until your potato is halfway submerged. When leaves have sprouted from your potato, gently twist them off and place them in their own bowl with water, covering the bottom. Roots will start to sprout from the bottom of your slip. When roots have reached 1″ long, slips may be planted. You can also take stem cuttings from established plants.
Slip/Cutting Depth: 6–12″. Bury up to the first set of leaves.
Space Between Plants: 12–18″
Space Between Rows: 2–3′
Sprouting Soil Temperature: 75–80°F
Days for Sprouting: 20–30
Start Indoors: 60–90 days before average last frost date.
Start Outdoors: Unless growing in tropical climates when stem cuttings can be planted directly in the soil, starting outdoors is not recommended. Transplant outdoors when all risk of frost has passed and soil temperatures are approximately 70°F or warmer.
Grows best in a tropical climate but can be grown as a warm season annual in cool regions or as a perennial in USDA Zones 9 and up. They’ll not tolerate frosts, so be sure to wait until soil is warm and forecasts look frost-free before planting.
Natural: Full sun to partial shade.
Artificial: Grows best under high pressure sodium HID lamps. Provide 11–13 hours of light daily for optimum development. Keep lights at least 6″ from the tops of plants to prevent burning.
SOIL: Prefers a well-drained sandy or loamy soil but will tolerate clay. If your soil is very heavy, you can plant in mounds to improve drainage and get better-shaped sweet potatoes. A pH between 5.5 and 6.5 will keep plants healthy and nourished.
SOILLESS: Grows well in soilless mixes with good drainage and aeration. We recommend using the barrel growing technique for best results. Drill small holes in the bottom of a plastic tub or barrel filled 1/4 to 1/2 way with a straight perlite/vermiculite mix. Add plants to the mix, cover your bin or barrel, and water frequently. Add a balanced fertilizer every few weeks if desired.
HYDROPONICS: Thrives in a variety of hydroponic systems.
AEROPONICS: Thrives in aeroponic systems.
Water: Requires low to moderate levels of water once established. Slips and cuttings must be kept moist while roots are forming. Aim for about 1 inch of water per week for mature plants. Be sure not to overwater, and cut back on watering in the week leading up to harvest.
Nutrients: Requires low levels of nutrients and can be grown on relatively poor soils. Feed plants once within a month after planting. Prefers higher amounts of potassium and phosphorus; avoid high-nitrogen fertilizers.
Foliar: Will benefit from a foliar feeding of liquid seaweed, or make a high-calcium spray by steeping eggshells in water for one month and diluting the resulting mixture.
Pruning: You can prune back excessively long vines, but it’s best to leave plants as large as possible.
Mulching: Use mulch around the base of young plants, particularly in dry, hot weather. Once established, the leaves will keep soil shaded and suppress weeds. In cooler climates, cover soil with a layer of dark material or clear reusable plastic to warm soil and allow for earlier planting in spring.
Deficiency(s): A boron deficiency can cause blistering as well as stunted growth.
Rotation: A 3- to 4-year rotation is recommended to keep soil healthy.
Companions: Grows well with okra. Sweet potato is kind of a bully, so avoid planting near other garden plants.
Harvest: Begin to harvest once vines begin to turn yellow. If growing in a cooler region, you need to harvest the whole crop before the first frost occurs. Use a garden fork to loosen soil and gently dig up the roots with your hands, taking care not to bruise or damage them. You can cut vines back before harvest for easier access to the soil. Sweet potatoes must be cured after harvest, by placing them in a warm (80–90°F) humid area for up to two weeks.
Storage: Covington sweet potatoes are valued for their extended shelf life and will store for up to 6–9 months without refrigeration if kept in a cool, dark location. A temperature of around 55 or 60°F is ideal. Don’t keep below 50°F, as this’ll cause damage.
Fun Fact: Although they share a name, sweet potatoes and potatoes are actually quite different! Aside from being in different families, potatoes are considered to be a true tuber while sweet potatoes are botanically thought of as a root. Sweet potatoes also don’t possess any “eyes,” which are a common feature on potatoes.
Preserve: Can be blanched and frozen, either in slices or mashed.
Prepare: Delicious baked, boiled, or made into a sweet casserole. The naturally high sugar content of these root vegetables will caramelize under high temperatures. You can also make your own sweet potato fries, mix slices into stir fries, or make a soup. Sweet potato pie is a popular dessert, or substitute sweet potato for pumpkin in other recipes. Young leaves and tender shoots can be mixed into a salad!
Nutritional: Provides vitamin(s) A, B-6, and C, as well as calcium, iron, potassium, manganese, and dietary fiber.
Medicinal: Contains high levels of the antioxidant beta-carotene, giving rise to their (usually) orange coloration. This may offer protection from certain kinds of cancer. As with many vegetables, regular consumption may help to decrease the risk of obesity, diabetes, and heart disease.
Sweet potatoes are often associated with winter holidays, with most recipes adding sugar, cinnamon, and butter to emphasize their sweetness. However, this veggie certainly has more to offer! Don’t believe us? Try this savory and definitely different Mediterranean Sweet Potato dish for a different take on an old favorite.