Gymnocalycium nigriareolatum is a species of Gymnocalycium from Argentina.
Gymnocalycium nigriareolatum is a cactus that grows either as a solitary plant or in clusters. It has dull, light to dark gray-green, rounded stems that are 4âÂÂ6 cm tall and 5âÂÂ8 cm wide (occasionally up to 12 cm). The plant typically has 10 sharp-edged ribs with shallow, transverse notches. It lacks central spines but has about 7 slightly curved, light gray-brown radial spines with darker tips. These spines are 1âÂÂ3 cm long, with the 3 lowest being the longest.
The flowers are funnel-shaped, either white with a pinkish throat or carmine red. They measure 4âÂÂ4.6 cm in length and up to 4 cm in diameter. The spherical fruits are small, about 1âÂÂ1.2 cm in diameter.
This species is native to the Sierra de Graciana and Cuesta de Los Angeles in the Catamarca province of Argentina, where it grows on rocky terrain at altitudes of 500 to 1500 meters.
It was first described in 1934 by Curt Backeberg.