A food crop primarily used in tropical southeast Asia and Polynesia. The scientific name of the edible species of taro is Colocasia esculenta; other common names include dasheen, gabi, cocoyam, and eddoe (sometimes written eddo or edda). It is a member of the Araceae family, which also contains the yautia. The most important use of taro is the harvest of its edible root (the corm), although its leaves are also edible. It is used as an ornamental plant in American and the UK.
Taro originated in southeast Asia, diffusing through India and the Pacific Islands (including Hawaii, where it is used to make poi). It was introduced into the Mediterranean during the time of the ancient Greeks, spreading southward into Africa. It has now spread to the west Indies and tropical America.
Taro is an important source of starch in many parts of the world. The root is about 20% starch (comparable to potatoes), and the starch granules are very small, aiding in digestion (estimated to be 98.8 digestibility). On the down side, taro contains more calcium oxalate (an irritant) than yautias, making them less preferred in many cases. Cooking or fermenting the taro will break down the calcium oxalate. Taro may be the most important root crop worldwide (in that is the primary food crop for many populations). Taro is best grown in wet, shaded areas, and are usually grown as an intercrop. It can be grown year-round in tropical climates, and the time of planting can be 'staggered' so that the pants will produce mature roots continuously throughout the year (it takes 14 to 18 month for a plant to come to maturity). The roots are a good source of carbohydrates, potassium, and provide some vitamins, particularly of the vitamin B complex, and protein. The leaves are comparable in nutritional value with spinach.
In the United States taro is used for baby food and baby formulae; it can be digested easily, even by people who are sensitive to cow milk.
Beside Colocasia esculenta, there are many other species of taro. These are primarily notable for their use as ornamental plants. Taro has large leaves, shaped like rounded arrowheads, supported by thick stalks. Most ornamental taro is grown in shallow water. While taro do have flowers, the plant and leaves are the main draw. Taro flowers are small, white or yellow (there may be other colours, but I haven't seen them), with rounded petals.
http://www.siu.edu/~ebl/leaflets/taro.htm is a good site.
http://www.grassrootsnursery.com/acatalog/Grass_Roots_Nursery_Taro__Colocasia_sp__4.html has pictures of ornamental taro.
I also used Plants For Man by Robert W. Schery (1972) for reference.