The Cactus Patch
Volume 8       March 2005      Number 3

The Genus Copiapoa
by L. M. Moe

The Atacama Desert of northern Chile is incredibly dry. It is the smallest desert of the world and it is also the driest. The average precipitation is less than 0.004 inch per year with some locations having no precipitation at all in over 400 years. This is the home of Copiapoa, the plant of the month.

Copiapoa is a fairly small genus of cacti with only about two-dozen species loosely related to Notocactus. Copiapoas are found only in the Atacama Desert, mostly near the coast. They were first collected in the 1820s and placed in the genus Echinocactus with all other globular cacti. It wasn’t until 1922 that Britton and Rose recognized the uniqueness of these plants and placed them into their newly described genus Copiapoa. The name comes from Copiapo, a town in northern Chile where many species occur.

These cacti vary in size from massive clumps (C. solaris) to one of the world’s smallest cacti (C. laui). Probably the most popular species is C. cinerea, sometimes called the compass cactus because they are small columnar cacti that lean or tilt towards the north. Apparently this helps reduce the internal core temperatures thereby lowering water loss.

Well-drained soil and infrequent watering are necessary to grow most Copiapoa species. In England, they are not watered at all from May through October. They do not tolerate freezing.

An excellent reference for natural history information is found in "Copiapoa in their Environment" by Rudolf Schulz and Attila Kapitany. Taxonomic information can be found in Edward Anderson’s "The Cactus Family." A good internet site for photos is to just enter "Copiapoa" into the Google image search field.

Copiapoa cinerea
photo by L. Maynard Moe

Stephen Cooley photographing Copiapoa cinerea
photo by L. Maynard Moe

Same guy behind the largest clump of Copiapoa solaris
photo by L. Maynard Moe

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