Its name derives from the Greek akantha , thorn and kallyx , buds, because the scales of the tube and ovary are modified in spines.

Depressed or flattened globular stem at the apex, dark green, up to 10cm high, and 10cm in diameter. Between 15 and 20 straight ribs and with tubers, provided with elliptical and felted arches, with the yellow-brown felt, but which with age become almost completely glabrous. 6-8 radial spines, sometimes more numerous, uneven, straight, or just barely curved, thick, conical and rigid. The central spines are generally arranged in a number of 2-3, but may also be solitary; the lower one is longer than all and is directed downwards, reaching even more than 4cm in length. At first they are all brown, then lighter and finally yellowish.

Acanthocalycium klimpelianum are relatively easy to grow and its large flowers make its cultivation worthwhile.

Its flowers form a crown around the apex, measure 6cm in length or more, 4cm in diameter, are pastel pink or white and are funnel-shaped. Globular ovary of 5x5cm, densely covered with pale yellow spiny scales with dark red base. The tube has a small woolly ring at the base, characteristic of all species of the genus. Spatulated outer teats, white with a pink middle band and dark brown mucron. Internal lanceolate sticks, white with a small brown mucron. Green throat stamens in a single series implanted primarily at the top of the receptacle; light green filaments, cream anthers. White wool ring near the base of the receptacle. Green style, light green stigma with approximately 11 lobes.
This cactus blooms between October and January.

The fruit is a spiny-looking ovoid berry, approximately 1cm in diameter, with a hard wall, with mucronated scales and persistent remains of the perianto. The dehiscence is vertical. The seeds are ovoid, with the testa finely warty, brown or blackish. The fruits ripen between February and April.

Light-Temperature:

Requires exposure to full sun, and does not tolerate intense cold
The lowest temperature (ºC) supported by this cactus is on average:: 0

Irrigation:

Very little water in winter. Regular watering in the summer.

Multiplication:

Seeds (with difficulty) or by stem separation.

References:

Pizzeti, Mariella. Cactus - Guias de La Naturaleza. Barcelona: Grijalbo, 1999.
Schuster, Danny. The World of Cacti: How to Select from and Care for over 1000 Species. New York: Facts on File, 1991.
Trevisson, Marcelo & Demaio, Pablo. Cactus de Córdoba y centro de la Argentina. L.O.L.A. (LITERATURE OF LATIN AMERICA), 2006.