This columnar, olive-green plants may reach up to 2 metres in height (2). The cylindrical columns are woody and upright, with 5 - 7 triangular ribs (2). Numerous cushion-like structures from which spines grow, known as areoles line each rib; they have a light brown to black covering of felt, with longer white or yellow hairs, and brown to reddish spines also originating from these points. At the tip of each column, the areoles become very dense so that there is a distinctive hairy covering (2). The woolly flower buds stand out against the green cactus with their dark blue coat, reddish spines and white hairs. When open, the white or pale cream petals are visible (2). Oval fruits then develop; the ribbed outer coat is also a dark purplish-blue, marked with areoles supporting spines and woolly tufts (2).
- Height: up to 2 m (2)