A rhizome is a specialized plant stem that grows horizontally, typically underground. While they might resemble roots, rhizomes are distinct because they possess features characteristic of stems, such as nodes and internodes. This unique growth pattern allows plants to spread and establish themselves across an area by extending their reach beneath the soil surface. Rhizomes are often referred to as “creeping rootstalks” due to their appearance and growth habit.
Anatomy and Biological Role
Rhizomes feature nodes from which roots and shoots can emerge. These nodes contain dormant buds that can develop into new plants, while adventitious roots anchor the plant and absorb water and nutrients. The internodes, or sections between the nodes, facilitate the horizontal growth of the rhizome.
A primary role of rhizomes is nutrient storage, serving as reserves for starches, proteins, and other vital compounds. This stored energy enables the plant to survive adverse conditions like winter cold, droughts, or disturbances, providing resources for regrowth when favorable conditions return. This storage capacity aids the plant’s long-term survival.
Rhizomes are also instrumental in vegetative propagation, a form of asexual reproduction. New, genetically identical plants sprout from the buds at the rhizome’s nodes. This allows plants to colonize new areas and regenerate, even if above-ground parts are damaged. This method offers an efficient way for plants to spread and establish populations.
Common Rhizome-Bearing Plants and Their Spread
Many familiar plants utilize rhizomes for their distinctive growth and spread. Ginger (Zingiber officinale) and turmeric (Curcuma longa) are prime examples where the commonly consumed “root” is actually a fleshy rhizome. These rhizomes grow horizontally, often forming compact clumps that are harvested for culinary or medicinal purposes. Buds on the ginger rhizome indicate points for new shoots and plants.
Bamboo is known for its aggressive spreading, largely due to its extensive rhizome system. Running bamboo varieties produce long, horizontal rhizomes that extend significant distances underground, allowing the plant to rapidly colonize. Even clumping bamboo, which spreads more slowly, relies on rhizomes to expand. These strong rhizomes can even push through cracks in hard surfaces, making them difficult to control.
Irises, particularly bearded irises, grow from rhizomes that lie at or near the soil surface. These thick rhizomes allow irises to multiply, forming new plants from the nodes. Gardeners often divide iris rhizomes every few years to prevent overcrowding and promote healthier flowering. This ease of propagation makes irises a popular choice for sharing among gardeners.