About Ariocarpus trigonus (F.A.C.Weber) K.Schum.
Ariocarpus trigonus typically grows as a solitary cactus, reaching up to 30 cm in diameter, though older individuals may form groups. It has numerous shiny brownish-gray-green warts, which are curved, acutely triangular on one side, and sharply keeled backward toward the base. These warts measure 3 to 8 cm long, and 1.5 to 2.5 cm wide at the base, with barely visible areoles on their slightly broken tips. This species has a very thick, beet-like root. Its numerous yellowish flowers, which grow up to 50 mm long and wide, form a wreath around the plant's woolly crown. Ariocarpus trigonus is native to the Mexican states of Nuevo León and Tamaulipas. It occurs on the eastern slopes of the Sierra Madre Oriental, north of Monterrey between Montemorelos and Linares, and in the Jaumave valley south of Jaumave. It grows on flat limestone hilltops in coarse, sandy-gravelly soil, at altitudes ranging from 500 to 1,200 meters.
