Sweet Potato

Other common names: Sweet Potato, Keledek, 番薯

Sweet potatoes are a versatile crop that produces both edible leaves and tubers, both of which are popular ingredients in a wide variety of Asian dishes. The leaves come in a range of shapes and colours including deep purple, neon yellow and green. Some of these attractive varieties such as the ‘Black Heart’ and ‘Margarita’ can be used to add a pop of colour to the garden.

This fast-growing perennial crop can be used as an edible groundcover or a living mulch to suppress weeds and protect soil from the sun and rain.

This vine is from the Ipomoea or morning glory family, and in the same genus as kang kong.

Sun and soil needs:

This vine thrives in both full and partial sun gardens and grows best with 4-8 hours of direct sunlight, but can also grow in 4- 6 hours of indirect sunlight but at a slower pace.

Plants do best in pots with loamy soil at least 30cm deep, or in true ground. The plant can be grown in smaller pots about 10cm deep but will not produce large tubers. Tuber growth can be encouraged by adding lots of organic material to the soil, making it soft.

This plant does best when watered regularly but will not survive waterlogging. It can tolerate drought for short periods of time, but the lack of water will reduce its growth.

As a fast-growing vine, this plant is traditionally left to sprawl on large patches of soil, but it can be also grown up a trellis. Regular pruning will encourage additional growth and improve air circulation.

Growing:

Sweet potato grows leaves and stems rapidly when fed with high nitrogen fertilisers, but this discourages it from growing tubers. Plants can be fertilised for the first two weeks after planting to help with its initial growth, and then left on its own to grow tubers after.

This vine grows large very rapidly and can climb up to 4m if a tall enough surface is available. Prune it back to manageable heights to make harvesting and maintenance easier.

Tuber growth is encouraged by stressing the plant. Leave vines unpruned, and occasionally flip them over to cause them to dry up.

Harvesting:

Plants can be harvested for leaves and stems, with younger leaves being the most tender. Most gardeners will begin harvesting leaves and stems from their Sweet Potato plant around two months after sowing from seed or after planting cuttings or tubers. Take note that the plant produces a milky sap when cut, and that the sap can irritate skin. Use gloves when pruning and harvesting leaves.

Tubers will take at least two months to form after the plant starts to produce vines, provided that the soil is soft and deep enough. Tubers can be left for up to 6 months to grow, after which they tend to be too tough and fibrous for eating.

Sweet potato is typically harvested multiple times by harvesting the younger leaves and stems as per the cut-and-come-again method. This plant can live for several years if cared for properly and will continue to produce new growth year round.

Harvest cycle:

Propagation:

This vine is usually grown via cuttings, or planting tubers. Stem cuttings can be rooted in water or soil. Tubers can be rooted in water or planted directly into the soil.

Common problems & solutions:

This plant is relatively resistant to pests and disease if kept healthy.

Sweet potato is vulnerable to fungal diseases that form leaf spots during the wet season or when the plant is overgrown. Increase air circulation with regular pruning and remove affected leaves to reduce the spread.

Rodents are attracted to and will dig up tubers to eat. Protect your plants with netting and fully bury tubers used to grow new plants.

Aphids, mealy bugs, whiteflies, and spider mites often infest the plant if it has underlying problems like repeated wilting from heat stress. Mechanical pest control methods like pruning the infested parts are the best methods for managing these pests in the short term, but resolving the underlying problem will prevent them in the long term.

Wilting leaves during hot weather is a sign of heat stress. Increase the number of times the plant is watered daily, and apply mulch at the base to prevent water loss.