Ube, or Dioscorea alata, is a species of yam distinguished by its vibrant purple flesh, a trait that has propelled it into global culinary popularity. This striking color comes from a high concentration of anthocyanins. Traditionally cultivated in tropical and subtropical regions, this vigorous, climbing vine is now successfully grown by gardeners outside its native range. Growing Ube requires attention to its tropical origins, particularly concerning soil composition and providing necessary vertical support for its extensive vine growth.
Pre-Planting Requirements
Ube is a tropical plant that thrives in heat, requiring a long, warm growing season for proper tuber development. Optimum temperatures for growth range between 77°F and 86°F (25°C to 30°C), and the plant cannot tolerate frost. In cooler climates, Ube must be grown as an annual, planted only after all danger of frost has passed and the soil has warmed considerably.
The plant performs best in full sun exposure, which fuels the rapid growth of its vine and maximizes tuber yield. While Ube tolerates various soil types, a deep, loose, and well-draining medium is important because the yam grows vertically downward. Heavy clay or compacted soil must be amended with compost and organic matter to ensure the developing tuber can easily expand. The soil should be fertile and consistently moist, mimicking tropical conditions.
Planting and Initial Establishment
Ube is typically propagated by planting small pieces of the mature tuber, known as setts, which function much like seed potatoes. Setts should weigh between 2 and 9 ounces (60 to 250 grams) and must include some skin area, as the growing points (eyes) are located near the skin. Before planting, cut surfaces must be cured or dried in a shaded, well-ventilated area until a protective layer forms; this prevents the sett from rotting in the soil.
Planting should occur in spring, once soil temperatures are reliably warm, usually a few weeks after the last expected frost date. Setts are planted shallowly, typically 4 to 6 inches deep, with the cut side facing down and the eye facing up. Setts should be spaced at least 2 feet apart to allow adequate space for the vine and the large underground tuber. Water the area thoroughly immediately after planting to settle the soil and begin the sprouting process, which can take three to twelve weeks.
Ongoing Care and Vine Management
The Ube vine is a heavy feeder and a vigorous climber, requiring diligent maintenance throughout the growing season. Consistent moisture is paramount, especially during the tuber bulking phase, which occurs three to five months after planting. Prolonged dry periods will significantly reduce the size of the developing yams, so supplemental irrigation, such as drip lines or soaker hoses, is beneficial.
Given the plant’s rapid growth, a robust fertilization schedule is necessary to support the extensive biomass. Begin feeding once the first shoots emerge, using a balanced fertilizer high in potassium to promote tuber growth. Repeat applications every 6 to 8 weeks through mid-autumn, or use a weekly diluted liquid fertilizer. Monitoring for pests like scale insects and root-knot nematodes is important, and crop rotation is advised to mitigate soil-borne issues.
Providing a robust, vertical support structure is crucial, as Dioscorea alata is a twining vine that can reach heights of 15 feet or more. The vine must climb for optimal tuber development, as this maximizes the leaf surface area for photosynthesis. Install a tall, sturdy trellis, arbor, or stake at the time of planting to prevent later root damage. Regularly train the rapidly growing vines onto the structure to ensure they are well-supported.
Harvesting and Curing
The Ube yam is ready for harvest once the plant signals the end of its growing cycle, typically 8 to 10 months after planting. This readiness is confirmed when the extensive foliage of the vine begins to yellow, wither, and completely die back. Harvesting before the vine dies back results in smaller, less mature tubers that do not store well.
Digging the tubers requires extreme care, as the Ube skin is thin and easily damaged, which can lead to rot in storage. Since the tubers grow vertically downward and horizontally away from the main stem, start digging a significant distance away from the vine base. Use a spading fork or shovel to loosen the soil, gently exposing the tuber without puncturing or scraping its surface.
Once lifted, the tubers require a brief curing period to prepare them for long-term storage. Lay the harvested yams in a shaded, well-ventilated area for a few days to allow the skin to dry and harden slightly, sealing any minor abrasions. This process improves storage life, allowing the tubers to be kept in a cool, dry place for several months.