Ipomoea batatas (L.) Poir.
(Convolvulaceae – the morning glory family)
common name: Sweet Potato
Ipomoea is from the Greek ιψ (ips), a worm, possessive form ιπος (ipos), and 'ομοιος (homoios), like; batata is the Haitian name for the plant. The first Europeans to taste sweet potatoes were the members of Columbus’s expedition of 1492. Later explorers found many varieties of the plant under an assortment of local names, but the name that stuck was the Haitian one. This name was later transferred to the ordinary potato, causing a confusion from which it has never recovered.
The sweet potato is the cultivated descendant of a wild plant whose tuberous remains have been found in a cave in Peru which was inhabited before 8000 BC. It was cultivated during the last few centuries BC, well before the time of the Incas. It was a staple food all over tropical America as far north as Mexico, as well as on the Caribbean islands. It is likely that, during the 13th century AD, it made its way to the Easter Islands and Hawaii, and then on to New Zealand in the next century. 16th century Spanish explorers took it to the Philippines, from where it was introduced into China to provide food in a serious famine in 1593. By the 18th century it had also made its way to Japan. Around the time of the American Civil War it was introduced to Africa, probably by slave traders, and ever since then it has been gradually replacing the yam as a major carbohydrate food in the tropical African diet. The sweet potato reached England in Elizabethan times via the Canary Islands, and it became the common potato of the English. A spin-off industry produced crystallized slices of sweet potato, which were sold with sea holly (Eringo) as an aphrodisiac. In Act V, scene v of The Merry Wives of Windsor, Falstaff (disguised as a stag) cries to Mistress Ford, “Let the sky rain potatoes; let it thunder to the tune of ‘Green Sleeves’; hail kissing-comfits and snow eringoes.”
The Sweet Potato is a perennial herb, cultivated as an annual, with trailing or winding stems up to about 4 m long that send roots into the soil at the nodes. Large fleshy edible storage roots are formed on the underground stem nodes. There are 2 broad categories of sweet potato – the staple type with white flesh and white or purple skin, with a high starch and dry matter content; and the dessert type with orange flesh and orange skin, with a high sugar and B-carotene content. There are numerous cultivars of each type.
The leaves are alternate, and either cordate or palmately lobed. The flowers are typical of the convolvulus family, with fused petals, usually white with a purple centre. The plants rarely flower where there are 11 or more hours of daylight. The seeds are used to raise plants for breeding purposes only.
The ‘potatoes’ are usually ready for harvesting between 18 and 22 weeks of planting (from vine tip cuttings), depending on the variety. The shoot tips and also the leaves can also be harvested, and used as vegetables. During World War 2, the sweet potatoes growing in Townsville back yards were very much a staple source of both carbohydrates and green vegetables after the population was quadrupled by the addition of Australian and US troops, and food became scarce.
Photographs © Donald Simpson, taken in Picnic Bay 2011