Sweet Potatoes are not really potatoes at all. The sweet potato plant is Ipomoea batatas which belongs to the family Convolvulaceae. Its tubers are important as a root vegetable. The young leaves and shoots are sometimes eaten as greens. Potato leaves, in contrast, are not edible.
The sweet potato is only distantly related to the potato (Solanum tuberosum). The softer, orange variety is commonly marketed as a yam in parts of North America, which differentiates it from the firmer, white variety.
The sweet potato is actually very distinct from the yam, which is native to Africa and Asia and belongs to the family Dioscoreaceae. The United States Department of Agriculture requires that sweet potatoes labeled as "yams" also be labeled as "sweet potatoes".
The genus Ipomoea also includes the garden flowers "morning glory".
Sweet potato varieties with dark orange flesh have more beta carotene, and their cultivation is being encouraged in Africa, where vitamin A deficiency is a health problem.
Under optimal conditions of 85 to 90% relative humidity at 13 to 16 °C (55 to 61 °F), sweet potatoes can keep for six months.
The plant does not tolerate frost. It grows best at about 75 °F, so in the UK it is restricted to greenhouses and frames. The crop is sensitive to drought at the point when tubers start to form, 50-60 days after planting. It is not tolerant of waterlogging.
Depending on the cultivar and conditions, tubers roots mature in two to nine months. With care, early-maturing cultivars can be grown as an annual summer crop in temperate areas. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are propagated not from tubers but by stem or root cuttings or by adventitious roots called "slips" which grow out from the tubers during storage.
As with potatoes, the true seeds are used for breeding purposes only.
ND / Diversity website
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