How to Grow, Harvest and Store Sweet Potatoes
by Jeffery Goss of Springfield, MO
Sweet potatoes do best in well drained sandy loam soil. Light loamy soils usually result in roots with better shapes than those grown in heavy or clay soils. But highest yields are generally produced on well-drained, clay-loam soils. Coarse, deep, sandy soils are generally low in fertility, subject to moisture stress and require more irrigation and fertilizer to grow a good crop. To prepare the soil, till well and apply 8-8-8 fertilizer at the rate of 2 lbs. Per 25 feet of row. Push the softened, fertilized soil into a foot-wide flat topped ridge row that is 8 inches high.
Plant slips 9 to 10 inches apart in the center of the ridge row, and at a depth of 3 inches with at least 2 plant nodes underground and two or more leaves above ground. Water well after transplanting. Thirty days after transplanting side dress with an 8-8-8 fertilizer again at the same rate (2 lbs. Per 25 feet of row) as roots begin to form in 30 to 45 days and they need nitrogen, phosphorus and potash for optimum growth.
Sweet potatoes require very little care. A bit of weeding, done carefully so as not to injure the shallow roots is usually all that is needed. Uncontrolled weeds can decrease the yields as much as 100%.
Harvesting of the sweet potato roots is usually done between 90-120 days or as soon as possible after a frost that has blackened the tops of the plants. A mature sweet potato will have 4 to 5 roots of varying sizes but the majority often should have a 1 ¾ inch diameter and be 3-9 inches in length. You can check for maturity by gently lifting the sweet potatoes out of the ground with a shovel making sure they do not become detached from the vine. If not ready to harvest, lower back down and cover with soil.
Dig sweet potatoes carefully as their skin is thin and they will bruise easily. It is best to wear gloves when handling them. Do not leave the roots exposed to direct sunlight with temperatures above 90 degrees F. for over 30 minutes as they will sun-scald and be more susceptible to storage rots. Once the sweet potato roots have been removed from the garden, spread them to dry for several hours away from direct sunlight. Once dry, put them in newspapered boxes and leave them in a dry, ventilated area for two weeks; then store in a cool, dry place (50-55 degrees F.) until you cook them.
Sweet potatoes can be stored for up to 10 months with little reduction in quality. Once they have been “cured” (usually after 2 months) they can be cooked and frozen for later home usage.
Late planting: Sweet potato slips can be successfully planted as late as the second week of July in most years (If your average first frost is October 25 or later). Water is very important with late-planted sweet potato slips, because the summer soil is apt to be very dry. Sweet potatoes actually benefit from hot weather, however, since they are a tropical crop.
Sweet potatoes should be harvested immediately after frost, lest they rot.