Typically considered a southern crop, sweet potatoes require 100 to 140 days to mature after transplanting to the garden. These tender plants do not tolerate frost and suffer when temperatures fall below 50 degrees Fahrenheit, making it difficult to grow these vining plants in northern climates. With the use of row covers to extend the season, sweet potatoes may reach maturity in northern climates. Sweet potatoes thrive in southern gardens and prefer rich well-drained soil with a pH between 5.0 and 6.5.
Prepare an area for sweet potatoes that receives full sun for the majority of the day. Six to 8 hours of direct sun is needed for these sun-loving plants to form thick meaty tubers.
Amend the soil with 4 to 6 inches of well-composted manure or compost to improve drainage and promote good aeration to supply roots with needed oxygen. Add 1 1/2 to 2 pounds of 16-16-8 fertilizer to each 100 square feet of gardening area. Work into the existing soil with a tiller or hand tools.
Mound the soil into a raised rows to a height of 8 to 12 inches and 6 to 8 inches wide, spaced 3 to 4 feet apart. This provides loose soil for the formation of tubers and promotes healthy growth.
Plant sweet potato slips 10 to 12 inches apart and firm the soil down with your hands to secure the plant. Water thoroughly to moisten the mound of soil. Keep soil evenly moist until new growth appears.
Mulch with organic matter to conserve moisture and prevent weeds. A 2 to 3 inch layer of leaves or hay makes an effective mulch.
Water when soil dries. Deep watering once a week is preferred to frequent light watering as light watering encourages roots to form close to the surface of the soil. The sweet potato is drought tolerant and suffers from heavy watering late in the season as it may cause tubers to crack.
Side dress with high nitrogen fertilizer, following the recommended application rate, in midsummer to promote vigorous vine and root development.