About Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose
Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose is a perennial succulent cactus. Plants are usually solitary, though they may sometimes form clumps. It typically reaches 6 to 10 centimeters in diameter and grows up to 50 centimeters (20 inches) tall. Its fleshy stem is blue or gray-green, has a somewhat felty texture at the top, and is often thorny. This cactus produces 8 to 13 straight or twisted ribs, each split into crookedly truncated cusps that grow up to 1.5 centimeters high. It has 9 to 18 marginal spines, which are either protruding or slightly curved and reach up to 3 centimeters long, plus 1 to 4 central spines that also grow up to 3 centimeters long. The central spines are brightly colored, appearing white or reddish in the middle, or red at the base and yellow at the tip, and gradually turn grayish as the cactus ages. The lowest central spine is extended and straight, while the upper central spines are erect and flat. Large, daisy-like flowers 5–8 cm (2.0–3.1 in) in diameter with ciliate edges bloom in summer. The petals are purplish-pink, fading to white toward their base, and the inner petal bases form a circle of red surrounding a prominent yellow center. The fruits are reddish-brown, scaly, and edible. This species is primarily found in the northern Chihuahuan Desert in Texas (United States) and the Mexican states of Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Tamaulipas, and Zacateca, growing at elevations between 800 and 2200 meters. It typically grows on flat gravelly soils, limestone or sandstone hill slopes or outcrops, and alluvial fans in desert or grassland environments. It is grown as an ornamental plant, requiring a warm, dry, sunny position in sharply draining specialist cactus compost. It has been awarded the Royal Horticultural Society's Award of Garden Merit.
