This variety is easily recognized by the very dark olive-green body and the strong, more numerous, longer, overlapping, spines that are white with a darker base.

Conservation status: Listed in CITES appendix 2.

Scientific name: Gymnocalycium gibbosum var. nobile (K. Schumann) Y. Ito, nom. inval. (Art. 33.1)
Published in Cacti 1952: 88,1952 = reductum

Common Name: Black Chin Cactus

Origin & habitat: This species is distributed in the mountains of Argentina of up to Patagonia .

Synonyms:

• Echinocactus gibbosus var. nobile K.Schum. 1898
• Gymnocalycium reductum (Link) Pfeiffer ex Mittler,
  Published in: Taschenbuch fuer Cactusliebhaber 2ed.: 48 + 124, 1844
• Gymnocalycium nobile n. n.
  Published in: Gymnocalyciums :66 (1978) = reductum
• Gymnocalycium gibbosum v. nobilis (Haworth) Borg

This variety is easily recognized by the very dark olive-green body and the strong, more numerous, longer, overlapping, spines that are white with a darker base.

Description: Solitary cactus.  Usually larger than the typical gibbosum.
Stem: Deep olive-green to almost black, flat  to almost spherical, 3-5(-10) cm tall, up to 12 cm in diameter, the apex is slightly woolly.
Ribs: 10-16 straight, divided in well distinct, angular ribs.
Areoles: Whitish-grey, elongated.
Radial spines: 7-10 (-12) 25-35 mm, strong, long, erect, overlapping, pastel-white (but also yellow or black), with a darker (reddish or brownish) base when young, that becomes whitish-grey as they age.
Central spines: 0-2 very similar to the radials.
Flowers: Infundibuliformin the nearest periphery just around the apex, 45-60 mm long, 60-65 in diameter. Tepals ivory white with a brownish mid rib or occasionally reddish.
Blooming season: Will flower without a distinct resting period.
Fruit : Globose or fusiform, 20-40 mm longgreen with white bordered scale.

Cultivation:This plant is a summer grower and pretty easy to cultivate.  Water and fertilize moderately in summer. It requires excellent drainage.  Make sure that soil gets the chance to dry out in between waterings.  During cold weather periods keep rather dry, but it can handle excessive water to little water.  Best for half-shade but it grows well in full sun and full shade, too (but in full sun it turns an uneven brownish red colour).
Frost Tolerance: Hardy down to  -12° to -32° C.

Propagation: Mainly through seeds.