Home Grown Vegetables

The Sweet Potato or Kumera

The sweet potato (Ipomea batatas) is an ideal choice for a home-grown vegetable. They belong to the Convolvulaceae or morning glory family and are not related to the common potato. Originally from South America, they are also known as kumera. They are important in the Pacific Islands as a dietary source of starch.

They are easy to grow, almost too easy as they will take over if you don't keep them under control. They are a fast growing vine with long trailing slender stems. Therefore they need a long warm growing season.

Sweet potatoCredit: Wikimedia

Sweet potatoes are a great substitute for normal potatoes and are very nutritious. They can be boiled, microwaved, roasted, steamed, fried or mashed – just like the humble potato. The young shoots and leaves can be used in stir fries and salads.

Sweet potato is easier to grow than the ordinary potato and you will have less problems with diseases and bugs. Sweet potatoes do not need a lot of water or fertiliser. In the garden, they are quick-growing, forming a great ground cover which will act like a living mulch to keep the temperature of the ground more consistent. The plant covers the ground and will eventually smother weeds.

The sweet potato is high in dietary fibre and energy. It is rich in sugar and Vitamin C and a good source of Vitamin A, Vitamin B, calcium, iron and beta-carotene. It has a low glycaemic index and high amounts of potassium. Sweet potatoes can have red, yellow or white flesh. Most popular is the red variety which has the highest Vitamin A content. Sweet potatoes are easily digested.

Sweet potato flowerCredit: Wikimedia

The sweet potato does best in well-drained, sandy loam soils. They need lots of sun and space and reasonable supplies of water and nutrients. Heavy, badly drained soils will result in misshapen tubers. Fertilisers high in nitrogen will result in lots of lovely leaves but very few tubers. A minimum frost-free growing season of 4 to 6 months is needed. Being semi-tropical it does best at temperatures between 20 and 30oC.

Sweet potatoes can be grown from a cutting. Take a piece about 30cm long, remove all bar the very last few leaves at the tip and cover the whole lot with soil except for the leaves. Roots will appear at the leaf nodes.

Another way is to buy a tuber and place the whole thing on the ground, cover with soil and keep moist. Shoots or slips will develop and these can be removed and planted out when they reach around 15cm.

A third way is to put a tuber upright in a container of water. Place the pointed end down and leave the top third projecting above the level of the water. Slips will grow from the eyes of the tuber and again, these can be removed and planted.

Slips can be planted about 30cm apart with around a metre between rows. Mulching around the plants and between the plants will help keep the weeds down until the plants spread sufficiently to form their own weed mat.

Although sweet potatoes like sandy soil, if the soil is heavy they can be grown on ridges or mounds. This allows adequate drainage. Sweet potatoes grown in heavy soil will develop tubers that are bent and/or forked. Mature compost can be dug in before planting. Water regularly until the plants are established. They will then get by with very little water. If you want to feed your sweet potatoes, seaweed extract is good or a light sprinkle of sulphate of potash.

Four to six months of reasonably warm weather is needed to allow sweet potatoes time to mature. Unfortunately sweet potatoes don't keep well so try to plant a few slips every few weeks. This way you can reap the benefits of the sweet potato for much longer.

To choose a tuber for the kitchen, look for a thickening of one of the original slips. Lift the plant carefully to get at the tubers at the base.

In the tropics, sweet potatoes can be afflicted by the sweet potato weevil. These metallic blue and orange insects are about 6mm long. The mature weevils eat all parts of the plant. They lay eggs in the roots and the larvae then attack the roots. Rotating vegetable crops will usually avoid problems with the sweet potato weevil.

As it is such a nutritious and delicious vegetable, it is worthwhile planting a sweet potato or two in your garden.