What Is a Rhizome? Understanding This Underground Stem

A rhizome is not a root—it's a thickened, horizontal stem that grows partially or entirely below ground. Roots emerge from its underside, while the primary growing point sits at one end, with additional buds forming along its sides. This structure allows the plant to spread laterally, forming new shoots and expanding its territory.

Classic examples of rhizomatous plants include bearded iris (Iris germanica), calla lily (Zantedeschia), and canna. A single rhizome can give rise to an entire colony over time, making these plants excellent for ground cover but sometimes aggressive in mixed borders.

When planting rhizomes, position them horizontally with the growing points facing up and the root side down. Ensure good drainage to prevent rot, and give them room to roam—or contain them with barriers if needed.