Colorado National Monument - Cactus

Colorado National Monument sits on the eastern edge of the Great Basin Desert. Unlike the more familiar deserts farther south, the hot arid summers in the Great Basin give way to freezing cold winter conditions. This presents some special challenges to the survival of succulent plants such as cacti.

Succulent plants have evolved the ability to quickly store water in specialized spongy tissues whenever moisture becomes available for use later in times of drought. This ability to store water can, however, create a serious plant survival problem during freezing cold weather. Moisture within the succulent plant tissues freezes, causing severe damage or death to the plant.

As winter approaches, cacti of the Great Basin Desert are able to reduce the moisture in their tissues to the point that they shrivel and go limp; some actually shrink down into the soil. The moisture remaining in the plant is altered so that the succulent plant tissues are not injured by freezing.

The return of spring warmth and moisture is all that"s necessary for these cold climate cacti to quickly and fully recover from winter dormancy.

Cacti are the most abundant type of succulent plant within Colorado National Monument. Visitors may find the following species:

Missouri Pincushion ( Escobaria missouriensis )

Porcupine Prickly Pear ( Opuntia erinacea )

Brittle Cactus ( Opuntia fragilis )

Purple-Fruited Prickly Pear ( Opuntia phaeacantha )

Cliff Prickly Pear ( Opuntia rhodantha )

Mountain Ball Cactus ( Pediocactus simpsonii )

Eagle Claw ( Sclerocactus parviflorus )

Claret Cup Cactus ( Echinocereus triglochidiatus )

Spineless Hedgehog Cactus ( Echinocereus triglochidiatus forma inermis )

Photographs and descriptions of most of the cacti listed above can be found in the following books sold at the visitor center:

Simon and Schuster"s Guide to Cacti and Succulents , edited by Stanley Schuler.

Cacti of the Desert Southwest by Meg Quinn

Most species are scattered throughout the monument, a few have more restricted habitats. Mountain Ball Cacti grow at the higher elevations. Missouri Pincushions and Spineless Hedgehogs are found in the southeastern portion of the monument.

The flowering season begins in the lower elevations in mid April, continuing into early July at higher elevations.