A rhizome (also known as rootstocks) is a type of plant stem situated either at the soil surface or underground that contains nodes from which roots and shoots originate (shown below). Rhizomes are unique in that they grow perpendicular, permitting new shoots to grow up out of the ground. When separated, each piece of a rhizome is capable of producing a new plant.
Rhizome, also called creeping rootstalk, horizontal underground plant stem capable of producing the shoot and root systems of a new plant. Rhizomes are used to store starches and proteins and enable plants to perennate (survive an annual unfavorable season) underground.
The primary function of the rhizome is the storage of nutrients, including carbohydrates and proteins, until the plant requires them for the growth of new shoots or to survive the winter in a process termed vegetative reproduction. Farmers use vegetative reproduction to laterally propagate plants such as hops, ginger, and various grass species. Some rhizomes are also consumed or used as a seasoning, including ginger and turmeric.
Examples of plants that are propagated this way include hops, asparagus, ginger, irises, lily of the valley, cannas, and sympodial orchids. Some rhizomes that are used directly in cooking include ginger, turmeric, galangal, fingerroot, and lotus.
By far the most dominant type of rhizome is the underground rhizome (pictured below), which is situated underground and includes ginger, hops, poison oak, grass species, and bamboo. Many of these plants have rhizomes that are consumed by humans (e.g., ginger).
While most rhizomes are situated underground, some plants have rhizomes that grow at the soil level or above (shown below). Examples of these plant species include ferns and irises.
The majority of rhizomes occur as a single layer from which shoots and roots originate. However, there are some plant species that form multiple layers in a complex network (e.g., Giant Horsetails).