Native to Asia, tropical Africa and northern Australia, the air potato (Dioscorea bulbifera)---also known as air yam, bitter yam and cheeky yam---was first seen in the U.S. in 1777 in Alabama. It is now found in Florida, Louisiana, Mississippi, Texas, Hawaii and Puerto Rico. While considered an invasive plant, the air potato can be cultivated for different uses.
The air potato is a twining vine that can grow to be more than 70 feet in length. It tends to overtake native plants that lie near the ground and often climbs to the tops of trees. They can grow up to 8 inches in a single day. The green, heart-shaped leaves grow on alternating sides of the stem. The air potato produces panicles that bloom with small white flowers. Tubers and bulbils (bulb-like growths at the leaf axils or stem base) develop both above and below ground. These two part of the air potatoes are the most utilized.
The underground tubers and bulbils of certain varieties of the air potato, such as sativa and rotunda, can be safely eaten. Others varieties are poisonous. The edible air potatoes found in Africa, Australia, Nepal and Thailand have a bitter taste, while the edible varieties cultivated in Asia are sweeter. Prepare the edible parts of the air potato by cleaning and peeling them. Boil, steam or bake the potatoes over coals. This process not only cooks the plant, but lessens the bitter taste. Some poisonous varieties can be detoxified through a long process of pounding the tubers with lime or sand, then slow roasting or repeatedly boiling them with ashes and, soaking them in running water. Toxic air potatoes should only be purified and eaten in times of famine or drought.
In the air potato's native environment, people use the plant in folk medicine. In India, bulbils are used to treat sores externally and hemorrhoids internally. People in Africa and Central Asia turn the tubers into a paste, which is used to treat snakebites and scorpion stings. China uses the tubers to soothe a sore throat, while Japan employs the tubers to treat diabetes. Some people in northern Bangladesh treat leprosy and tumors with air potato tubers. While the furanonoditerpenes and glycosides in the tubers may have anti-tumor properties, further research is needed. No other medicinal uses of the air potato have been scientifically proven.
Toxic air potatoes are also used as a poison. They contain alkaloids, saponins, sapogenins and tannins that can make humans or fish ill. In parts of Africa, as wells as Java, people grate the above-ground tubers into a stream when they hunt. The poison released into the water stuns the fish, allowing the hunters to capture them. Farmer who cultivate edible air potatoes sometimes mix in toxic air potato plants with their crops, hoping to discourage thieves from stealing from their fields.