Gymnocalycium ANDREAE - Gymnocalycium andreae, Andrea's chin cactus.
Gymnocalycium is a genus of plants in the cactus family (Cactaceae), comprising about 70 species widely distributed across South America, especially in Argentina, Brazil, Paraguay, Uruguay, and Bolivia at elevations of 800-3000 m (2625-9843 ft) above sea level, on granite and clay soils.
Gymnocalyciums are valued for the elegant outlines of their stems, usually globose and flattened, with a diameter of 4-15 cm (1.6-5.9 in), with height being roughly half of the diameter. The primary stem coloration varies from grayish-green to brownish-green, sometimes with an almost gray or almost brown tint. Some cultivars feature unusual red or yellow stems lacking chlorophyll; such plants are capable of developing only in a grafted state. The stems are typically distinctly ribbed, with tubercles situated along the ribs. The spines are moderately stiff, often recurved.
The plants are prized for their showy flowering. The flowers are funnelform, with a short tube, developing from areoles at the stem apex and opening during the day. Unlike most other cacti, flower tubes in members of this genus lack bristles and hairs and are covered with smooth scales. Coloration varies from white and pink to red, yellow, greenish, or brownish-yellow. The fruits are oblong, juicy or dry, containing large black seeds with a texture characteristic of the genus.
Gymnocalycium andreae has a medium-sized stem, about 5 cm (2.0 in) in diameter, dark, bluish-green, clustering, with 8 ribs. The shape is flat to rounded. It has 6 to 10 whitish spines brownish at the base, of which 1-3 central spines are of the same length as the others or shorter, blackish-brown, later turning gray. The flowers are 4.5 cm (1.8 in) across, light yellow. Flowers appear in abundance even on small plants.