Sclerocactus glaucus (K. Schum) L. Benson is western Colorado cacti that is proposed endangered on the Federal Register list of endangered plants. This “brill” cactus is very little known! only rarely finding its way into cactus books or plant manuals. Its usually solitary stems have a squat, flattened globe appearance, growing only two to four inches tall. There are 7 to 11 spines at each “eye” (areole)
of the stem. Most of the spines are white, with the exception of one long, brown spine, called the lower central spine, which comes straight out of the center of each eye. The spine-covered eyes of are at the tip of nipple-like structures, tubercles. In mature plants, the tubercles are aligned into vertical rows called ribs. Each Sclerocactus glaucus stem typically has 12 ribs.

This rare cactus is found in west-central Colorado and northeast Utah. In Colorado it grows at about 4,500 to 5,500 feet. It blooms for a brief period in early spring. The flowers are a deep pink, with many petals, many stamens, one style and a lobed stigma. The stamens and stigma become “ripe” at different times, which ensures that cross-pollination of the flower takes place.

If the bright, showy flowers of Sclerocactus glaucus are not present to give a clue to its location, the plant is very difficult to see because its squat appearance and drab spines blend into the surrounding soil and rocks. Even while it is blooming, one can walk through Sclerocactus glaucus’s habitat in the morning and see very few, if any, of its stems. If the same area is walked over after the flowers open in early afternoon, many stems will be found. This evasive cactus blooms in the afternoons for a period of about two weeks, then seems to vanish into the surrounding terrain until it blooms again a year later.

Sclerocactus glaucus’s elusive nature during most of the year protects it somewhat from the most serious danger to rare cacti in the Southwest–over-collecting by cactus dealers and hobbyists. This exploitation first became a problem in Arizona,