Sweet potato is a perennial that is usually grown as an annual. It grows from underground tuberous roots with trailing, twisting stems that can be as long as twenty feet (six meters). Leaves are variable in shape, size, and color but are generally more or less heart-shaped and green with purple markings. The single flowers are funnel shaped and white or pale purple but are rarely seen in temperate regions. Roots grow where stem nodes touch the ground, and most develop into the edible storage roots, usually four to ten storage roots per plant.