The Colorado hookless cactus is a barrel shaped cactus that ranges from 1.2 to 4.8 inches (3 to 12 centimeters) tall, with exceptional plants growing up to 12 inches (30 centimeters) tall. Stems range from 1.6 to 3.6 inches (4 to 9 centimeters) in diameter. The stems have eight to 15, typically 12 or 13, ribs that extend from the ground to the tip of the plant. Along the ribs are areoles, which are small, cushion-like areas, with hooked spines radiating out, as described by Heil and Porter in 2004. There are two types of spines - radial and central - defined by the size and position on the plant (74 FR 47112). The two to 12 radial spines are located around the margin of the areole, and extend in a plane that is parallel to the body of the plant. The radial spines are white or gray to light brown. They are up to 0.67 inches (17 millimeters) long, and less than 0.04 inches (1 millimeter) in diameter. The one to five central spines, usually three, are 0.5 to 2.0 inches (12 to 50 millimeters) long, are generally longer than radial spines and extend from the center of the areole. The central spines include abaxial and lateral forms. Abaxial spines are typically single, point toward the top of the plant and are noticeably bent at the tip at an angle usually less than 90 degrees. Lateral spines are usually present in pairs on either side of the abaxial spine, but are more or less straight and diverge from the abaxial spine at an acute angle, usually 20 to 50 degrees. The flowers are usually funnel-shaped, but sometimes bell-shaped. They usually have pink to violet tepals, that are petal-like flower parts which are not differentiated into petals and sepals, with yellow stamens, the male reproductive organ of the flower, and are 1.2 to 2.4 inches (3 to 6 centimeters) long and 1.2 to 2 inches (3 to 5 centimeters) in diameter. The fruit is short, barrel-shaped 0.31 to 0.47 inches (8 to 12 millimeters) wide and 0.35 to 1.2 inches (9 to 30 millimeters) long.
Pollination is likely carried out by a broad assemblage of native bees and other insects, including ants and beetles.
Populations of Colorado hookless cactus occur primarily on alluvial benches, meaning soils deposited by water, along the Colorado and Gunnison rivers and their tributaries. Colorado hookless cactus generally occurs on gravelly or rocky surfaces on river terrace deposits and lower mesa slopes. Exposures vary, but Colorado hookless cactus is more abundant on south-facing slopes, as noted by the Colorado Natural Heritage Program. Soils are usually coarse, gravelly river alluvium above the river flood plains, usually consisting of Mancos shale with volcanic cobbles and pebbles on the surface. Elevations range from 3,900 to 6,000 feet (1,400 to 2,000 meters), as documented by Heil and Porter in 2004. Associated desert shrubland vegetation includes shadscale (Atriplex confertifolia), galleta grass (Pleuraphis jamesii), black-sage (Artemisia nova) and Indian rice grass (Achnatherum hymenoides). Populations also exist in big-dominated (Artemisia tridentata) sites and in the transition zone from sagebrush to pinyon-juniper (Pinus edulis and Juniperus osteosperma) communities.
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