Growing Food: A Guide to Food Production

LIMITATIONS

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store they are prone to become either rotten and/or damaged by insects, rodents,

usually of a mild degree.

Sweet Potato

Ipomoea batatas

Sweet potatoes have a great range of types, and show wide variety in characteristics,
but basically there are two types, based on the consistency of the tubers when they
are cooked. The one type has firm, dry, mealy flesh which is normally yellowish or
purplish; the other type has a softer, moist, whiter flesh—often incorrectly called
“Yams”, especially in the USA. Hundreds of named, improved varieties of both
types are available.

So

T he plant is perennial but is usually cultivated as an annual. It is a member of the
Convolvulaceae (morning glory) family; the flowers are monoecious (male and
female flowers both on the same plant).
In the subtropics and temperate regions the tubers are mainly harvested all at the
same time, then stored for winter use and subsequent planting. In the tropics stem
cuttings are taken and planted during virtually 12 months of the year.
me varieties produce trailing or twining stems 5 metres or longer, and the leaves
are very variable between varieties; even on the same plant older leaves may look
very different from younger ones.
B oth the tuber and the aerial parts are eaten, and sweet potatoes are an important
part of the diet in many tropical countries. Sweet potato tubers contain the pigment
beta-carotene, which the human body can convert into Vitamin A. The tubers con-

In 2004 more than 127 million MT were grown, according to FAO. The biggest
producers are China, Asia, Africa, North and South America, Japan and New Zealand.

212 TONY WINCH

Potatoes are susceptible to many diseases, especially Blight.

The growing plants need quite specific temperature conditions as well as a

regular rainfall pattern or irrigation.

Low protein content of about 2% (though the protein is richer in lysine than

cereals).

The crop is labour intensive to cultivate, especially in unmechanized systems.

The tubers are bulky and expensive to transport, 80% of the weight is water. In

etc.

All green or sprouting plant parts contain poisonous glycoalkaloids, known as

Yam (North America) Patate Douce, Patate de Malaga (French); Susskartoffel
(German); Papa Dulce (Latin America); Batata de Malaga, Boniato, Camote
(Spanish); Batata douce (Portuguese); Batatas (Arabic); Kamote (Philippines);
Kumala (Fiji); Shakarkandi (Hindi); Mucur Dinish (Tigray); Tafach Dinich
(Ethiopia); Usambé, Katata {Katito—small} (Angola); Kachalu-e Shirin (Dari)

solanine, which may cause acute nausea, vomiting, diarrhoea & prostration,

tain about 16% starch, 6% sugars and are a good source of Vitamin C (23 mg/100 g).