Rhizome: Definition and Examples

A rhizome is a horizontal underground plant stem that sends out roots and shoots from nodes. In some plants, a rhizome is the only stem. In others, it is the main stem. Plants use rhizomes to store food and for vegetative propagation.

Examples of Plants With Rhizomes

A wide variety of plants have rhizomes. Rhizomatous grasses include bamboo, pampas grass, caterpillar grass, and Bermuda grass. Flowering plants include irises, cannas, lily of the valley, and sympodial orchids. Edible plants include asparagus, hops, rhubarb, ginger, turmeric, and lotus. Aspen trees spread via rhizomes. Although the trees of an aspen stand appear distinct, they are all connected underground and may be considered the largest organisms on Earth. Other plants that use rhizomes include poison oak, poison ivy, the Venus flytrap, and ferns.

Rhizome vs. Stolon

Rhizomes are commonly confused with stolons. A stolon or runner sprouts from a stem, has long spaces between nodes, and produces shoots at its end. A familiar example of a plant with stolons is a strawberry plant. Strawberries often extend stolons above ground. As the plantlets at the end of the stolon grow, gravity pulls them down. As they near the ground, roots grow and attach the new plant. Rhizomes have less distance between nodes and new shoots and roots can grow anywhere along their length.

Rhizome vs. Roots

Rhizomes are sometimes called creeping rootstalks. The word "rhizome" even comes from the Greek word that means "mass of roots." Yet, rhizomes are stems and not roots. The main difference between a rhizome and a root is that a root has no nodes or leaves. Roots function to attach plants to the ground, store food, and absorb water and nutrients.

Unlike roots, rhizomes transport water and nutrients to other parts of the plant. Like roots, rhizomes and stolons sometimes store food. Thickened portions of rhizomes or stolons form stem tubers. Potatoes and yams are edible stem tubers. Cyclamen and tuberous begonias grow from stem tubers. In contrast, root tubers are thickened parts of the root. Sweet potatoes, dahlias, and cassavas grow from root tubers. While stem tubers often die back in the winter and produce plants in the spring, root tubers are biennial.

Difference Between Rhizomes, Corms, and Bulbs

Stem and root tubers, corms, and bulbs are underground storage units that are collectively called geophytes. But, they are different from one another:

• Rhizome: Rhizomes are underground stems. They may produce stem tubers.
• Corm: Corms are rounded stems that are flattened. They have a basal plate from which roots emerge. Leaves emerge from the other end. Corms store food, which is exhausted as the plant grows. The original corm shrivels and a new one is produced for the following season. Freesia and crocus grow from corms.
• Bulb: Bulbs are layered with a basal plate for roots and a pointed end that produces leaves. New bulbs can form around the original bulb. Examples of bulbs include onions, tulips, and daffodils.

Propagating Plants With Rhizomes

It's often easier to propagate a rhizomatous plant using rhizomes rather than seeds or spores. A rhizome may be cut into pieces and each section can give rise to a new plant if it has at least one node. However, stored rhizomes are susceptible to rot from fungal and bacterial infections. Commercially, rhizomes may be grown using tissue culture. For the home gardener, non-hardy rhizomes may be dug up and stored over the winter to replant in the spring. Rhizome propagation is aided by the plant hormones jasmonic acid and ethylene. Ethylene is easy to find, as ripening apples and bananas release it.

Sources

• Fox, Mark, Linda E. Tackaberry, Pascal Drouin, Yves Bergeron, Robert L. Bradley, Hughes B. Massicotte, and Han Chen (2013). "Microbial community structure of soils under four productivity classes of aspen forests in Northern British Columbia." Ecoscience 20(3):264–275. doi:10.2980/20-3-3611
• Nayak, Sanghamitra; Naik, Pradeep Kumar (2006). "Factors effecting in vitro microrhizome formation and growth in Curcuma longa L. and improved field performance of micropropagated plants." Science Asia. 32: 31–37. doi:10.2306/scienceasia1513-1874.2006.32.031
• Rayirath, Usha P.; et al. (2011). "Role of ethylene and jasmonic acid on rhizome induction and growth in rhubarb (Rheum rhabarbarum L.)." Plant Cell Tissue Organ Culture. 105 (2): 253–263. doi:10.1007/s11240-010-9861-y
• Stern, Kingsley R. (2002). Introductory Plant Biology (10th ed.). McGraw Hill. ISBN 0-07-290941-2.