Sweet Potato

Overview

Sweet Potato - Ipomoea batatas

Sweet potatoes are sub-tropical crop, related to the ornamental Morning Glory. They grow best in warm, humid conditions but several varieties have been bred that do well in the UK; these are Beauregard, Bonita or Carolina Ruby. Sweet potatoes are usually available as slips; these are the shoots that have sprouted from a tuber and started to root up. If your slips look dehydrated when they arrive place then in a glass of warm water to revive. Pot up your slips in individual pots  in March or early April with the stem of the slip is buried right up to the base of the leaves. Then water the pots and place them in a warm propagator to establish, which will take about three weeks. Grow them on indoors until the frosts are over and it’s warm enough to plant them outside.

How to grow

It is possible to grow sweet potatoes outside in the warmer parts of the country, in a sheltered spot. If growing in the cooler regions you will need to grow them under cover in Polytunnels or the Greenhouse. To give your sweet potato seedlings a good start, warm the soil up several weeks before planting by covering it with black polythene from late March or early April. In late May/early June, make slits in the polythene, spaced 1metre (1ft) apart and plant your young plants in the ground through these slits. Water regularly and feed fortnightly with a high-potassium liquid plant food (tomato feed is ideal). Sweet potatoes are climbing plants, so one option is to train the stems up canes or a trellis as they grow, if left to sprawl nip out the growing tips to encourage side shoots.

How to Harvest

Sweet potatoes should be ready to harvest approximately sixteen weeks after planting, which is usually in October or November. If you live in one of the cooler areas, and you are growing in a poly-tunnel or greenhouse, then you can usually harvest tubers sooner than those grown outside. Tubers are ready to harvest when the stems and leaves have turned yellow, or the early autumn frosts have blackened the foliage. Cut the stems at the base,  clean away the excess foliage and carefully lift the tubers. Once lifted lay the tubers on some sacking or sheeting for a few days in the sun to `Cure` the tubers before storing; if a cold or frosty night is forecast move the tubers indoors at night. Alternatively you can `Cure` them indoors in a warm room at a temperature of 23-29C (75-85F). This method of Curing will harden the skins and extend the storage life of the tubers as well as help sweeten their flavour. Make sure all tubers that are stored are sound and unblemished to reduce the risk of any fungal storage rots. Unlike normal potatoes, Sweet potato tubers are best stored in a warm place no cooler than 10-15C (50-60F). If stored too cold or the tubers become frosted; this will affect the flesh texture and eating quality of tubers. Stored correctly Sweet potatoes should keep for several months.

Sweet Potatoes have a number of uses in the kitchen. The Sweetest of the flesh can be eaten raw, but is usually eaten boiled, steamed, baked, fried, mashed or even batter fried. The dried roots are also excellent chopped up then mixed with wheat flour and made into interesting bread and cakes. You can even eat the leaves and tips of the young shoots as a substitute for spinach.

Issues

Fortunately sweet potatoes do not suffer from many pests or diseases. The only pests they are troubled with occasionally are whitefly in the greenhouse or aphids; these usually attack the fresh young succulent tips of the foliage. Aphids can be controlled using a suitable insecticide or organic soft soap. Also during wet weather the foliage may get a slight attack by slugs or snails, which can easily be controlled, using one of the various Slug controls available.