Sweet potatoes, scientifically known as Ipomoea batatas, are vining root vegetables distinct from the common white potato. Unlike regular potatoes, which are grown from seed pieces or “eyes,” sweet potatoes are propagated from sprouts called “slips.” These slips are young shoots that emerge from the mature storage root and are the necessary planting material for a new crop. Successfully growing sweet potatoes begins with a common grocery store purchase, as store-bought roots can be used to generate these slips.
Selecting and Preparing the Sweet Potato
Selecting the sweet potato from the market is crucial for successful sprouting. Choose organic sweet potatoes, as conventionally grown roots may be treated with sprout inhibitors that prevent slip development. Look for a healthy, medium-sized potato free of blemishes, soft spots, or decay.
If the potato appears dormant, a conditioning period can help. Allow the root to sit in a warm, dark place for about one to two weeks before sprouting begins. This brief period mimics commercial curing conditions, helping to break dormancy.
Generating the Slips
The process of generating planting slips uses two primary methods, both requiring consistent warmth and light. The popular water method involves suspending the sweet potato in a jar so the lower half is submerged. Use three or four toothpicks inserted around the middle of the potato to rest on the rim of the container, keeping the potato stable.
The jar should be placed in a warm location, ideally maintaining 75°F to 85°F, such as on a heat mat or near a sunny window. Roots will emerge from the submerged end, followed by green shoots from the top half. Change the water every few days to keep it fresh and prevent the root from rotting.
A second, often faster, method is the soil or sand method, where the sweet potato is buried halfway in a container filled with moist potting mix or sand. Keep the container warm and consistently moist, but not saturated, to encourage both root and slip development.
Once the slips reach four to six inches in length and have a few leaves, they are ready to be detached from the mother potato. Carefully twist or snap the slips off where they emerge from the root. Since detached slips are typically rootless, place them in a glass of water to develop a strong root system before planting. After one to two weeks, the slips will form a visible mass of fine white roots, indicating they are ready for the garden.
Planting the Rooted Slips
The timing of planting the rooted slips is governed by soil temperature, as sweet potatoes are highly sensitive to cold. Slips should not be moved outdoors until all danger of frost has passed and the soil temperature consistently reaches at least 65°F at a depth of four inches. Planting too early in cool soil can stunt growth or cause the slips to rot.
Sweet potatoes thrive in loose, well-draining soil, ideally a sandy loam, which allows storage roots to expand easily. Incorporating organic matter, such as compost, improves soil structure. A slightly acidic pH between 5.8 and 6.0 is optimal for reducing common diseases. Planting in raised beds or hills helps the soil warm up quickly and provides better drainage.
Plant the slips by burying the stem deep enough so that all developed roots and lower nodes are covered, leaving only the top few leaves exposed. Space the slips approximately 12 to 18 inches apart, allowing ample room for the vigorous vines to spread. Immediately after planting, water the slips thoroughly to settle the soil around the new roots. Consistent moisture is necessary for the first week to encourage establishment.
Harvesting and Curing the Crop
Sweet potatoes typically take 90 to 120 days of warm weather from planting until the roots are ready for harvest. A common signal of maturity is when the leaves and vines begin to turn yellow, though roots continue to grow until the first hard frost. Harvest must occur before the soil temperature drops below 50°F, as cold soil can damage the roots and negatively impact their quality and storage life.
To harvest, use a garden fork to carefully loosen the soil about 18 inches from the main stem to avoid puncturing the roots. Gently lift the sweet potatoes from the soil, handling them delicately. Do not wash the harvested roots; allow them to dry for a few hours, then gently brush off any excess soil.
The final quality of the sweet potato depends on curing, a process necessary to convert starches into sugars and heal minor skin damage. Curing involves holding the roots in a high-heat, high-humidity environment for four to seven days. Ideal conditions are 80°F to 85°F and 90 to 95 percent relative humidity. This process significantly improves the flavor, texture, and long-term storage capability of the sweet potatoes.