Let the Punishment Fit the Yam

What we call yams in this country, as food writers never tire of pointing out, are really varieties of sweet potato. True yams belong to the genus Dioscorea and are grown in tropical and subtropical parts of the world from West Africa to the islands of the South Pacific to Central America and the Caribbean, which cultivates a local yam called cush-cush or yampee. Even Japan, not a warm country by any means, has its own glutinous yam, yama-no-imo, which is not only eaten by itself but also used in making the buckwheat noodles called soba. Buckwheat flour lacks gluten, and without imo, soba noodles wouldn’t hold together.

Root vegetables such as yams provide carbohydrates just as grains do, and they probably were cultivated before grains. They have certain advantages over grains, such as the fact that the edible part is an underground tuber, which is safe from animal and insect pests. (But not from human pests. A 14th century Arab visitor to West Africa recorded that “rustling� yams from somebody else’s yam field was punishable by beheading.)

Starchy tubers such as yams are substantial food sources. In fact, they’re really the plant’s own store of nutrition. So plants often protect them from potential diners by making them poisonous.

The cassava plant, from which we get tapioca, is one plant with a tuber that is poisonous unless carefully washed and cooked, and some yams are poisonous too. In West Africa, certain yams were traditionally used as a source of poison for arrowheads. Actually, you wonder why they didn’t use yam poison, rather than beheading, to punish yam rustlers. It would seem more fitting.