Mesa Verde Cactus

Sclerocactus mesae-verdae

Description

Mesa Verde cactus,Sclerocactus mesae-verdae,usually grows as a single spherical stem, 1.5-3 in (3.8-7.6 cm) in diameter, but may form clusters of up to 15 stems. Eight to 11 straw-colored or gray spines, 0.25-0.5 in (6.4-12.7 mm) long, form radial clusters, typically without central spines. The color of the cactus allows it to blend into its surroundings.

The plant bears creamy yellow to greenish-white flowers, 0.75 in (1.9 cm) in diameter, from late April to early May. A green fruit forms late in May, browns with age, and splits open at the end of June to release black seeds. The major pollinator is believed to be a metallic green sweat bee belonging to the family Halictidae. No other pollinators have been observed.

Seedlings have been found at all population sites. Often seeds germinate adjacent to the parent plant. Given the large number of seeds produced per plant and the actual number of seedlings observed, it is apparent that the success rate for these seedlings is very low.

The species is closely related to the Wright fish-hook cactus (S. wrightiae ) and to the Brady pincushion cactus (Pediocactus bradyi ), both of which are federally listed as endangered. It has also been known by the scientific names Coloradoa mesaeverdae, Echinocactus mesae-verdae, and Pediocactus mesae-verdae.

Habitat

Mesa Verde cactus grows on the Colorado Plateau in the floristic province of the Navajoan Desert. It is generally restricted to the Mancos and Fruitland shale formations—alkaline soils with "shrink-swell" properties that make them harsh sites for plant growth. These clay formations erode easily, forming what are known locally as badlands (low rolling hills with sparse vegetation). This cactus is most frequently found growing at elevations of 5,280-6,600 ft (1,609-2,012 m) on the tops and slopes of hills.

Distribution

Mesa Verde cactus was first discovered near Cortez, Colorado, in 1940 and is considered endemic to the Navajoan Desert of San Juan County, New Mexico, and of Montezuma and possibly Montrose Counties, Colorado.

A major population of the Mesa Verde cactus is located on the Ute Mountain Indian Reservation in Colorado. Other populations have been noted near Waterflow, New Mexico, and at several sites on the Navajo Indian Reservation between Shiprock and Sheep Springs. Indian reservation lands are administered in part by the Bureau of Indian Affairs (BIA).

The total population of the Mesa Verde cactus is 5,000-10,000 plants, but the species is not evenly distributed throughout its range. It grows in dense clusters within certain favorable subhabitats.

Threats

The Mesa Verde cactus, like most other endangered cacti, has suffered at the hands of collectors; very few mature plants can still be found in the wild. Even European and Asian tourists seem to know right where to find the cactus and, along with commercial collectors, are depleting the population, especially during flowering season when the plants are easier to spot. The Mesa Verde cactus is difficult to cultivate, especially in areas of high humidity, because it rots very easily. As many as 90% of the plants collected rot and die within the first year, so collectors are not truly "collecting" the cactus, they are killing it.

Habitat disturbance is also a threat. Oil and gas exploration, livestock trampling, road maintenance, and off-road vehicle use have all taken a toll on the Mesa Verde cactus. Because many cacti grow on the tops and sides of hills, off-road vehicles crush and uproot plants and seedlings when following the high ground.

Conservation and Recovery

Better enforcement of laws and international trade agreements against the collection and trade of endangered species would greatly benefit the Mesa Verde cactus. Monitoring journals and commercial plant catalogs will also help to identify and prosecute violators. At least 70% of the population of the Mesa Verde cactus lies within the Navajo Nation and another 20% within the Ute Mountain Indian Reservation. Recovery efforts will require the cooperation and assistance of both tribal councils and the BIA.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

References

U. S. Fish and Wildlife Service. 1984. "Mesa Verde Cactus Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.

Weniger, D. 1970. Cacti of the Southwest. University of Texas Press, Austin/London.

Weniger, D. 1984. Cacti of Texas and Adjacent States. University of Texas Press, Austin/London.