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Plant Highlight: Cleistocactus icosagonus

October 2013

Cacti with golden yellow spines are always appealing, especially when the light catches the spines and sets them aglow. A fine example is Cleistocactus icosagonus, from the Andes in northern Peru and southern Ecuador. Though presently included in the genus Cleistocactus, this species has at various times been put in other genera, including Seticereus, Borzicactus and Loxanthocereus.

Cleistocactus icosagonus is a clumping species with cylindrical stems which are initially upright and eventually sprawling to the side with the end portion erect. The stems can attain a length of up to 2 feet (60 cm) or more, with a diameter of 1¼ to 2¼ inches (3 to 5.5 cm). They are densely covered in golden yellow spines. On younger stems the spines are quite short, but once they get old enough to flower the spines become longer and bristly.

At the Ruth Bancroft Garden, Cleistocactus icosagonus begins flowering in summer and produces multiple flushes of blooms through to early fall. The tubular red-orange flowers, 2¾ inches long (7 cm) and flared at the mouth, emerge a little below the ends of the stems. The golden spines together with the red-orange flowers makes a vivid impression. In other forms of the species the flower color ranges from orange to red, and the flower length may be up to a little over 3 inches (8 cm).