Rhizome
A stem that grows sideways at or under the soil surface, sending up shoots along its length.
A rhizome is a horizontal stem. It stores food, roots from its underside and sends up leaves and flowers from buds along the top. Bearded irises have fat rhizomes that sit half out of the soil. Cannas, lily of the valley and ginger spread by rhizomes too. The sacred lotus grows from long rhizomes in the mud of ponds, and these are eaten as lotus root across Asia. Gardeners propagate such plants by cutting the rhizome into pieces, each with a bud.