The short stout, cylindrical stems are completely covered by thick, gold-colored spines that obscure the green skin and give a fuzzy appearance, becoming dark brown or even black with age. Both spines and stem segments are easily detached, adhering to anything that moves, and can be difficult to removing owing to tiny reverse barbs; this characteristic is the main method by which the plant is propagated, when fallen branches take root. Mature cacti are around 5 feet tall, usually surrounded by a ring of discarded spines, pads and flowers.