Old man cactus earns its name from the long white spines that give mature plants a frosted, whisker-covered look. It grows slowly into a columnar form 12–18 inches tall, a quiet sculptural presence on a sunny sill.

Bright indirect or direct light through a window, water sparingly when the soil is completely dry, and provide good air circulation. These are low-fuss plants that ask only to be left alone between waterings.