Potato

Solanum tuberosum

Edible Uses

Edible Parts: Tubers.

Root - raw or cooked. Potatoes are a very versatile food that can be used in a wide variety of ways. Having a mild flavour, and readily accepting the flavour of other foods, they can be eaten on a regular basis without becoming boring. Whilst occasionally eaten raw, they are most commonly cooked and can boiled, baked, fried, added to soups, stews etc. The cooked potato can also be dried and made into a powder and then used as a thickener in soups etc, or be added to cereal flours when making bread, biscuits etc. The potato is a very rich source of starch, but does not contain high quantities of other nutrients. When exposed to light, the skin turns green and contains the toxin solanine. Whilst eating a small quantity of green potato is unlikely to cause harm, it is probably wisest to remove any green part of the tuber before eating it. The fresh petals of white-flowered varieties contain 0.2% rutin.

Medicinal Uses

Whilst mainly used as a staple food, potatoes do also have a number of medicinal virtues. A juice made from the tubers, when taken in moderation, can be helpful in the treatment of peptic ulcers, bringing relief from pain and acidity. Excessive doses of potato juice can be toxic - do not drink the juice of more than one large potato per day. A poultice has been made from boiling potatoes in water. This is applied as hot as can be borne to rheumatic joints, swellings, skin rashes, haemorrhoids etc.

Peeled but uncooked potatoes have been pounded in a mortar and then applied cold as a soothing plaster to burns and scalds. Potato skins are used in India to treat swollen gums and to heal burns. The tubers contain very small quantities of atropine alkaloids. One property of these alkaloids is the reduction of digestive secretions, including acids produced in the stomach. The root and leaf diffusates of growing potato plants possess cardiotonic activity. Dried ethanol extracts of above-ground parts of the plant show marked hypotensive and myotropic action and a spasmolytic and soothing effect on intestinal musculature. Ethanol extracts of the leaves have antifungal properties, active against Phytophthora infestans. The leaves, seeds, and tuber extracts show antimicrobial activity against Gram-positive and Gram-negative bacteria. The leaves are antispasmodic.

Other Uses

Cleanser, polish, size, starch.

The tubers are a source of starch that is used in sizing cotton and to make industrial alcohol etc. It also has many other uses in industry. Ripe potato juice is an excellent cleaner of silks, cottons and woollens. The water in which potatoes have been boiled can be used to clean silver and to restore a shine to furniture. Emollient and cleansing face masks are made from potatoes, these are used to treat hard, greasy and wrinkled skins. The potato is a good source of biomass. When boiled with weak sulphuric acid, potato starch is changed into glucose and this can then be fermented into alcohol.

Cultivation details

Succeeds in most soils, preferably in a sunny position. It performs well on a wide variety of soils, sandy loams, silt loams, loams, and peats. Tubers rot in wet or heavy clay soils. Prefers a slightly acid soil, the tubers are subject to scab on limy soils or those deficient in humus. Yields are best from plants grown in rich soils with plenty of organic matter. The plant is reported to tolerate an annual precipitation in the range of 9 to 410cm, an annual temperature in the range of 3.6 to 27.8°C and a pH of 4.2 to 8.2. Potatoes are a cool weather crop, the optimal temperature for growth being 15 - 20°C for most cvs. Growth of the tubers is best at soil temperature of 17 - 20°C, with usually no tubers formed above 32°C. The top-growth of this species is not frost hardy, though the tubers will tolerate a few degrees of frost if left in the ground. Potatoes are very widely grown throughout the world for their edible tubers, there are many named varieties.

The potato is one of the main staple foods, it is very high yielding (50 tonnes or more per hectare have been achieved in some European countries, though at the other extreme yields of little more than 2 tonnes have been achieved in parts of Africa), stores well and can be available all year round. The potato probably arose through cultivation from several wild species that can still be found growing in S. America. Many of these wild species can be used in breeding programmes for improved disease resistance etc. Does well when grown after a crop of rye, Secale cereale. Grows well with legumes, sweet corn, cabbage, marigolds, horse radish, flax, dead nettles, sainfoin and nasturtiums. Grows badly with tomatoes, sunflowers, members of the cucumber family and raspberries. Potatoes should not be stored with apples because the ethylene gas released by the apples will cause the potatoes to go soft and develop a sour taste.

Propagation

The normal way of growing potatoes is from tubers. Harvest when the leaves yellow, select even sized, 5 cm tubers for seed, and store seed in a dry, light place, and, before planting, lay in a dry, dark place for a week to sprout.