Plants are usually solitary. It is also
highly variable in appearance. In fact, there are a number of form so
different looking, that only some authorities recognize the different
populations as segregate varieties.
Stem: Globose or flattened to cylindrical, up to 20 tall, 13 cm
in diameter. The apex is depressed and often deprived of spines.
Blue-green, tan-green to dark violet-green .
Ribs: 13 to 17 cm, about 7 to12 mm tall in adult specimens,
Areoles: 5-20 mm apart.
stiff and curved upwards and inward, pale
yellowish, brownish to dark grey. (bright red when very young) later
grey. The var. kunzei is described with very thin, needle-shaped spines
but it grows and merges with the thick spined form. And in cultivation
it is possible to find bolt thick and thin spined specimens.
Central spines: 1 to7 about 2-5 cm long with a darker tip.
Radial spines: 10 to 15 about 1,5-4 cm long straighter, mostly
directed upward, the upper of them are longer than other.
Roots: Fibrous or tuberose.
Flower: Up to 3,5 cm long widely opened, whitish, dull-pink to
pale-brown whit red veins. Petals have often a darker mid-line.
Fruits: 2 x 1,5 cm oval, fleshy, hollow, dull-green, tan, to
reddish that opens at maturity by a basal pore.
Seeds: 1,25 mm.