About Cleistocactus hyalacanthus (K.Schum.) Rol.-Goss.
Cleistocactus hyalacanthus (K.Schum.) Rol.-Goss. grows as a shrub with erect shoots that branch from the base. Shoots grow up to 1 meter tall and 4 to 6 cm (1.6 to 2.4 in) in diameter, with 15 to 20 ribs that have areoles spaced 5–8 mm (0.31 in) apart. This cactus has approximately 3 central spines that are brown to yellowish, and reach up to 3 cm (1.2 in) in length. It also has 20 to 30 unequal fine radial spines that are bristly and whitish. Flowers emerge from the center of spine clusters near the apex of the stem. They first appear as small dark spots, then gradually enlarge over one week to ten days into purple-pink flowers that are 3.5 to 4 cm (1.4 to 1.6 in) long and 5–7 mm (0.28 in) wide. Each flower only opens slightly, and for just one day. The bracts of the flowers are spread out. The flowers are eaten by hummingbirds, which are attracted to their vivid red color. Fertilized flowers develop into fruit. The spherical fruits are light greenish, and range in color from brick-red to orange. They reach a diameter of about 1 to 1.2 cm (0.39 to 0.47 in), contain white flesh, and turn yellow when fully ripe. The fruits are eaten by larger birds, which disperse the small black seeds in their droppings. Cleistocactus hyalacanthus is distributed in the wooded dry forests of the Argentinian provinces of Salta and Jujuy, growing at altitudes between 1700 and 3100 meters. It may also be present in southern Bolivia.
