A rhizome is a horizontal stem of a plant that forms new roots and shoots. Many invasive plants form rhizomes, making them difficult to eradicate. When cut from the parent plant, the rhizome forms a new plant, unlike many roots that die.
Many types of plants, including lilies, crabgrass, iris and ginger propagate by means of rhizomes. The rhizome of the ginger plant is the root that cooks use as a spice. Some rhizome tissue stores starches, as in the case of true arrowroot. In ferns and water lilies, the rhizome is the only stem the plant forms.
Gardeners often use rhizomes known as rootstock in the propagation of plants, such as asparagus, lily of the valley and cannas as well as some orchids, through vegetative reproduction. Rhizome propagation is a form of asexual reproduction, with the resulting plant being genetically identical to the parent plant. Because the plants are genetically identical, they produce the same color of flowers without variation.
Other plants form underground stems that propagate the plant without forming rhizomes. Bulbs, corms, runners and tubers are all underground stems, but each differs from the rhizome. White potatoes are tubers, and while they form new stems from the eyes, they do not produce the buds like those found in rhizomes.