Twisted ribs cactus

Description

Solitary cactus (unless injured) until very old age, or with few branches from ground level when old. This specie has a tuber-like taproot but it is not a geophyte as the apical meristem is above ground.Stem: Cylindric to club-shaped, or spherical, up to 17cm tall, 5-8 cm in diameter. Seedlings and immature plants often have narrowly cylindrical stems. With age, the stems broaden distally.Spines: Radial spines 13-28 per areole, translucent yellowish, tips red-brown, longest spines 6 to 28 mm long; central spines 3-4 per areole; abaxial central spine tan to whitish 1 per areole, hooked terete or slightly flattened, generally whitish or light brown, 12-38 mm long; adaxial central spines (2-)3 per areole, brown to dark reddish brown, erect, straight, 19-50 mm long. Juvenile spines are all radials numerous, short, tightly appressed and pectinately.Roots: Long, fleshy, tuber-like taproots with bulbous swellings, sometimes having bulbous secondary roots, frequently horizontally oriented.Flowers: Bright green to yellowish (rarely pink to pale reddish) with a brown midline. Flowering in February-March.