Wednesday, 29 June 2016

Sweet potato (Ipomoea batatas)

The sweet potato (Ipomoea batatas) is a perennial herbaceous vine, usually grown as an annual in the UK. It belongs to the Convolvulaceae family. It is also known as kumara, camote, Brazilian arrowroot, kau kau and yam. Please note that the name yam is also used for a variety of other plants, particularly other edible tubers from the Dioscorea genus (Dioscoreaceae family).

Sweet potato (I. batatas)



















The sweet potato is one of the most widely cultivated staple crops in the world. The botanical origin of its domestication remain unclear. Some suggest wild tuber-bearing populations may have been domesticated independently in South America and the Caribbean/Central America.

Growing methods

Plants are grown from 'slips' which are cuttings taken from the mature sweet potato itself. In the UK these are quite widely available for purchase from plant catalogues. More recently cell grown plants have become available which have already been rooted.

Once the slips arrive they should be placed in pots with multi-purpose compost. Keep them watered and cover with a polythene bag until they are rooted. They can then be potted on as required and planted out in May or June when the soil is warm and the risk of frost has passed. Plants do well in neutral or acid soils rich in potash. Ensure the soil is moist and free draining. Plant in a sunny sheltered position and avoid shady areas. Alternatively, grow in a polytunnel or greenhouse.

Once the slips have rooted plant them up in pots.



















Foliage can be left to grow along the ground or trained up canes, string or frames to save space.

If planting outside, cloches and fleece provide extra warmth which helps the plants thrive. Alternatively they can be grown through slits under a polythene film. Temperatures of between 23ºC and 26ºC are best for tuber production. Plants require less than 11 hours daylight to flower but daylength has little affect on the production of tubers. Plants can be overwintered in a frost-free greenhouse, polytunnel or windowsill.

Tubers take four to five months to mature. They rot if they are frozen. They don't store very easily and so should be consumed once they have been lifted which is when the leaves turn yellow and die back.

Species have been developed for growing in temperate areas such as the UK. Supermarket tubers may not produce slips as they are often treated with an anti-sprouting spray. Also bear in mind that supermarket tubers will have probably been grown in a different climate to the UK so any slips taken from these tubers may not thrive here.

Other uses

The sweet potato plant is used to make arrowroot, biomass, alcohol and as animal feed. Some Ipomoea species are grown as ornamental plants. Fibres from the plant can be used to make biodegradable plastic. The roots can be used as a potato substitute and the leaves as a spinach substitute.

Raw edible parts

The young shoots, the leaves and the tubers are all edible raw.

Issues

A trypsin inhibitor occurs in the shoots, leaves, stems and tubers of sweet potatoes and some references claim that because of this we should not eat them raw. Trypsin is an enzyme that helps with protein digestion. Most of the literature about this refers to animal feed where animals are not fed a varied diet. The North Carolina Sweet Potato Commission recommends eating sweet potatoes raw. Sweet potatoes are native to North Carolina and this region is one of the largest producers in America.