Some stems grow sideways underground instead of upward. A rhizome is a horizontal stem that runs beneath the soil surface, sending up new shoots and roots at intervals. Irises, ginger, cannas, and many grasses spread this way, forming expanding clumps over time.

Rhizomes store food and allow the plant to colonize new ground. Gardeners propagate these plants by cutting the rhizome into sections, each with at least one bud or growing point. Planted at the correct depth, the pieces quickly establish independent plants.

In the garden, rhizomatous plants can be vigorous. Some stay neatly in place; others need occasional division to prevent overcrowding. Understanding the underground habit helps when placing them and when controlling spread. The structure itself is usually firm and fleshy rather than fibrous.

• Horizontal underground stem
• Produces new shoots and roots
• Stores nutrients for the plant
• Used for vegetative propagation