Yams belong to the genus Dioscorea and are distinct tuber crops with a starchy, often drier texture, unlike sweet potatoes. Precise timing is essential for successful cultivation, as harvesting at the correct stage impacts the tuber’s quality, storability, and flavor. Harvesting too early prevents the full development of starch. Waiting too long can cause the tuber to begin its next growth cycle, compromising its texture and leading to watery tubers that spoil quickly.
Visual Cues Indicating Readiness
The primary indicator that a yam tuber is ready for harvest is the natural dieback, or senescence, of the vine. This process involves the plant redirecting energy and stored carbohydrates from the leaves and stems into the underground tuber. The leaves will yellow, wilt, and eventually dry out, signaling the end of the active growth phase.
Vine dieback usually occurs eight to ten months after planting, depending on the species and climate. Harvesting should commence once 90 to 95% of the foliage has dried up, indicating the tuber has maximized its size and starch content. Harvesting for storage requires full maturity, allowing the tuber to enter its natural dormancy period.
Tubers intended for immediate consumption can sometimes be harvested slightly earlier. Some growers use “yam milking,” carefully removing a mature yam while leaving the tuber head to regenerate a second, smaller harvest. For extended storage, waiting for complete dieback ensures the tuber skin is firm and the flesh is dense.
Proper Techniques for Digging Yams
Yams develop deep into the soil and are often large and irregularly shaped, requiring a delicate digging process to prevent damage. The yam’s thin skin is easily bruised or cut; any break creates an entry point for rot during storage. The goal is to extract the entire tuber with its skin intact.
Start by cutting back the dried vines and clearing the area around the yam hill. Since tubers can grow deep and spread far, begin digging at least 12 to 18 inches away from the vine’s base to avoid slicing the tuber. Use a sturdy digging fork, spade, or specialized bar to loosen the soil in a wide circle around the plant.
Carefully work the tool under the tuber’s estimated location, pushing the soil away gently rather than prying immediately. Feel around the tuber to determine its shape and depth before attempting to lift it. Once the soil is loose, use the tool to create leverage and slowly lift the entire tuber. Any yams that are cut or bruised should be set aside for immediate consumption, as they are unsuitable for long-term storage.
Curing and Storing the Harvest
After harvest, yams must undergo curing, a post-harvest treatment that heals minor scrapes and toughens the outer skin layer. Curing promotes the formation of a hard cork layer, preventing moisture loss and minimizing microbial infection, which extends the tuber’s shelf life. This process should begin immediately after the yams are harvested and cleaned of excess soil.
Curing Conditions
Optimal curing requires high temperature, ideally between 32°C and 40°C (90°F to 104°F), combined with high relative humidity (85% to 95%). Under these conditions, curing takes between one and four days; higher temperatures shorten the duration. Curing can be achieved by piling yams in a shaded area and covering them with grass or mats. Drape the pile with a canvas or jute bag to trap heat and moisture, ensuring the cover does not touch the tubers.
Long-Term Storage
After curing, yams are ready for long-term storage in a cooler environment to maintain their dormant state. Ideal storage conditions involve a temperature around 13°C (55°F) and a relative humidity of 85% to 90%. Stored yams should be kept dry and well-ventilated. Place them on elevated shelves or racks to prevent ground contact and encourage air circulation, ensuring viability for months.