Stem Tubers

A stem tuber is a swollen underground storage organ that forms from a thickened rhizome or stolon. The top or sides of the tuber produce shoots that grow into stems and leaves, and the underside produces roots. Stem tubers have a vertical orientation with one or a few vegetative buds on top and fibrous roots extending from the bottom. (Think back to grade-school science when you stuck wooden toothpicks into a sprouting potato and elevated it in a jar with the bottom of the potato immersed in water. Placed in a sunny window, the potato sent out roots from the bottom and buds from the top.) Tubers typically store large amounts of starch, a valuable food source with a high-energy value.