Starting a garden from a grocery store purchase is a practical way to begin food self-sufficiency. Tubers bought from the produce aisle contain the biological potential to sprout entire new plants. By following specific preparation and planting steps, a single store-bought item can yield a significant harvest for your kitchen. This process works especially well for warm-season root vegetables that grow readily from sprouts.
Clarifying Your Tuber: Yam Versus Sweet Potato
The first step in growing from a store-bought tuber is understanding its botanical identity, which is often confused in the grocery store. The vast majority of items labeled as “yams” in US markets are actually sweet potatoes (Ipomoea batatas), a member of the morning glory family. True yams (Dioscorea species) are botanically unrelated, featuring rough, scaly skin and a dry, starchy interior. Sweet potatoes, by contrast, have smooth, thin skin and moist, sweet flesh.
The instructions below focus on growing sweet potatoes, which are typically what is purchased. True yams are rarely found outside of specialty markets and require a much longer, hotter growing season and deep soil, making them difficult for the average home gardener. Sweet potatoes are grown as a warm-season annual and are much better suited for most temperate climates.
Preparation for Planting: Creating Slips
The sweet potato itself is not planted directly into the garden; it must first produce sprouts known as “slips.” A single tuber can generate dozens of these slips, which are the actual starts for new plants. To maximize success, choose an organic sweet potato, as conventional ones are sometimes treated with sprout inhibitors.
There are two primary methods for encouraging slip growth: the water method or the soil method. The water method involves suspending the sweet potato partially in a jar of water, often using toothpicks for stability. Placing this setup in a warm, sunny location encourages roots to form in the water and shoots to sprout from the top, a process that takes four to eight weeks.
The soil method is often preferred because it promotes immediate root formation and can cut down on the time required. This technique involves burying the sweet potato halfway on its side in a container of moist potting mix, kept warm and well-lit. Once the shoots are about six inches long with several leaves, they are ready to be detached from the parent tuber. If the detached slips lack sufficient roots, place them in a glass of water for a few days until white roots emerge before transplanting.
Cultivation, Ongoing Care, and Harvest
The rooted slips should not be planted outdoors until all danger of frost has passed and the soil temperature is consistently above 65°F. Sweet potatoes thrive in full sun and require a long, warm growing season. The ideal soil is sandy, loose, and well-draining, as heavy clay soil can restrict root growth.
Plant each slip 12 to 18 inches apart, burying the stem deep enough to cover the roots and the lower half of the slip. Sweet potato vines can reach five feet or more in length; they can be left to sprawl or trained up a trellis to save space. Consistent moisture is important, especially during dry periods, but avoid overwatering as the tubers are susceptible to rot.
Tubers are ready for harvest between 90 and 120 days after transplanting. A key sign that the crop is ready is when the vines begin to yellow and die back in the early fall. It is important to harvest before the first hard frost, as cold soil temperatures can damage the tubers.
Cut back the long vines a few days before digging to encourage the roots to toughen their skin. Use a garden fork to gently loosen the soil about a foot away from the main stem to avoid damaging the delicate tubers. After lifting the sweet potatoes, they must be “cured” by keeping them in a warm, humid environment (typically 80–85°F) for about ten days. This curing process heals any nicks, converts starches to sugars, and prepares them for long-term storage in a cool, dark place.