Rhizome.

A modified stem, commonly growing horizontally at or below the surface, that can store resources and produce shoots and roots.

What it means for your plants

Do not confuse every thick underground structure with an ordinary root. Handle storage structures carefully when repotting and avoid unnecessary injury. Species with water reserves often need thoughtful dry-down periods.

Put it into practice

Care for Zamioculcas zamiifolia with realistic light expectations, a draining pot, and attention to its water-storing rhizomes.