Sclerocactus glaucus
Author: (J.A. Purpus ex K. Schum.) L. Benson

Colorado hookless cactus

Cactaceae (Cactus Family)

Close up of Sclerocactus glaucus by Gina Glenne
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Close up of Sclerocactus glaucus by Gina Glenne
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Close up of Sclerocactus glaucus by Lori Brummer
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Ranks and Status

Global rank: G2G3
State rank: S2S3
Federal protection status: USFWS Threatened
State protection status: None

[+] Description and Phenology

Please see 1997 profile

General description: A squat, globular, spiny succulent. Each mature stem is 3-12 cm tall, 4-9 cm wide; the largest observed was 24 cm tall x 14 cm wide (DeYoung 2010). However, during the driest part of the year the stem may shrink to below ground-level. Central spines are straight (hookless). The plants are inconspicuous except when in flower (April-May), when showy, fragrant, pink to magenta flowers appear at the top of the stem.

Look Alikes: Distinguished from Scelerocactus parviflorus by the absence of a strongly hooked central spine (Weber and Wittmann 2012). 

Phenology: Plants are readily visible when flowering, usually late April and early May. After flowering, their dull greyish green color makes them difficult to see. During extended dry periods the stems may shrink to below ground level. Fall rains may cause them to swell up again and become easier to see (Spackman et al. 1997).

[+] Habitat

Habitat of Sclerocactus glaucus by Peggy Lyon
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Habitat of Sclerocactus glaucus by Peggy Lyon
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Populations occur primarily on alluvial benches along the Colorado and Gunnison Rivers and their tributaries. Sclerocactus glaucus generally occurs on gravelly, or rocky surfaces on river terrace deposits and lower mesa slopes. Exposures vary, but S. glaucus is more abundant on south-facing slopes. Soils are usually coarse, gravelly river alluvium above the river flood plains usually consisting of Mancos shale with volcanic cobbles and pebbles on the surface. Elevations range from 1200-2000 m. Associated vegetation is typically desert scrub dominated by shadscale (Atriplex confertifolia), galleta (Hilaria jamesii), black-sage (Artemisia nova), and Indian rice grass (Stipa hymenoides). Other important species include two similar spherical or cylindrical cactus species, strawberry hedgehog cactus ( Echinocereus triglochidiatus var. melanacanthus) and Simpson's pincushion cactus (Pediocactus simpsonii). Other important species in the plant community include the prickly pear cactus (Opuntia polyacantha), winterfat (Krascheninnikovia lanata), yucca (Yucca harrimaniae), snakeweed (Gutierrezia sarothrae), low rabbitbrush (Chrysothamnus viscidiflorus), sand dropseed (Sporobolus cryptandrus), and Salina wildrye (Elymus salinus) (USFWS 1990, Scheck 1994). Fire is not typically characteristic of S. glaucus habitat, but areas with large infestations of cheatgrass (Bromus tectorum) may build up sufficient fuel to carry fire into S. glaucus populations.  
Exposed, gravel-covered, clay hills, saltbush or sagebrush flats, or pinyon-juniper woodlands; 1400-2000 m (Flora of North America Editorial Committee 2003).

Elevation Range: 4,646 - 7,126 feet (1,416 - 2,172 meters)

[+] Distribution

Distribution of Sclerocactus glaucus in Colorado.
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Colorado endemic: Yes
Global range: Known from Delta, Garfield, Mesa, and Montrose counties in Colorado. Estimated range is 3307 square kilometers (1277 square miles), with the northern population covering 505 square kilometers, and the southern population 2802 square kilometers. Values calculated in GIS by the Colorado Natural Heritage Program in 2017 following NatureServe methodology.

[+] Threats and Management Issues

Summary results of an analysis of the status of Sclerocactus glaucus based on several ranking factors. This species was concluded to be "weakly conserved”. From Rondeau et al. 2011.
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Habitat destruction or modification by development of energy extraction, water storage projects, transportation, and residental facilities constitutes the greatest threat to S. glaucus. This threat is wide-ranging, increasing, and less amenable to mitigation than are the threats of illegal collecting or disturbance by agricultural or recreational activities. The scope and severity of this threat are inferred from numbers of plants known to be impacted by projects such as the TransColorado gas transmission pipeline and Colorado Highway 50 widening, as well as anecdotal observations from field personnel familiar with the species. Cheatgrass (Anisantha tectorum) invasion is also causing considerable degradation of S. glaucus habitat in some areas.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Benson, L. 1982. The Cacti of the United States and Canada. Stanford University Press, Stanford, California. 1044 pp.
    • Dawson, C. 2009. Personal communication with Colorado Natural Heritage Program staff regarding BLM rare plant monitoring in Colorado.
    • Denver Botanic Gardens. 2008. Demographic monitoring of Sclerocactus glaucus, an Endemic Species of western Colorado. Population Monitoring 2007-2008. Technical Report to Bureau of Land Management, U.S. Department of Interior.
    • Ecology Consultants, Inc. 1978. An illustrated guide to the proposed threatened and endangered plant species in Colorado. U.S. Fish and Wildlife Service, Lakewood, CO. 114 pp.
    • Elliott, B. A., S. Spackman Panjabi, B. Kurzel, B. Neely, R. Rondeau, M. Ewing. 2009. Recommended Best Management Practices for Plants of Concern. Practices developed to reduce the impacts of oil and gas development activities to plants of concern. Unpublished report prepared by the Rare Plant Conservation Initiative for the National Fish and Wildlife Foundation.
    • Ferguson, J. 2003. Personal communication with CNHP staff.
    • Flora of North America Editorial Committee. 2003. Flora of North America North of Mexico. Vol. 4, Magnoliophyta: Caryophyllidae, part 1. Oxford University Press, New York. 559 pp.
    • Franklin, B. 2003. Personal communication with Colorado Natural Heritage Program.
    • Heil, K.D., and J.M. Porter. 1994. Sclerocactus (Cactaceae): A revision. Haseltonia 2:20-46.
    • Hochstatter, F. 1997. The genus Sclerocactus (Cactaceae) - Part 4. Cact. Succ. J. Gr. Brit. 15: 74-81.
    • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
    • Lambeth, Ron. 2003. Personal communication with Colorado Natural Heritage program staff.
    • Lyon, P. 2003. Personal communication with Colorado Natural Heritage Program.
    • Mayo, E. 2009. USFWS communication with Colorado Natural Heritage Program staff.
    • Neale, J.R. and M. DePrenger-Levin. 2010. Demographic monitoring of Sclerocactus glaucus,an endemic species of western Colorado. Population Monitoring 2007-2010Technical Report to Bureau of Land Management, U.S. Department of Interior. Prepared by Denver Botanic Gardens.
    • Neely, B., S. Panjabi, E. Lane, P. Lewis, C. Dawson, A. Kratz, B. Kurzel, T. Hogan, J. Handwerk, S. Krishnan, J. Neale, and N. Ripley. 2009. Colorado Rare Plant Conservation Strategy, Developed by the Colorado Rare Plant conservation Initiative. The Nature Conservancy, Boulder, Colorado, 117 pp.
    • O'Kane, S.L. 1988. Colorado's rare flora. Great Basin Naturalist 48(4): 434-484.
    • Peterson, J.S. 1982 Plant species of special concern. Unpublished manuscript.
    • Porter, J. M., M. S. Kinney, and K. D. Heil. 2000. Relationships between Sclerocactus and Toumeya (Cactaceae) based on chloroplast trnL-trnF sequences. Haseltonia 7: 8-23.
    • Robertson, E. 2009. Center for Native Ecosystems personal communication with Colorado Natural Heritage Program staff.
    • Rocky Mountain Society of Botanical Artists. 2009. RARE Imperiled Plants of Colorado, a traveling art exhibition. Exhibition catalogue developed by the Denver Botanic Gardens and Steamboat Art Museum.
    • Scheck, C. 1994. Special Status Plants Handbook Glenwood Springs Resource Area. Unpublished report prepared for the Bureau of Land Management, Glenwood Springs, CO.
    • Schneider, A. 2013. Wildflowers, Ferns, and Trees of the Four Corners Regions of Colorado, New Mexico, Arizona, and Utah. Accessed on-line at
    • Smithsonian Institution. 1980. Draft abstracts on rare plants. Unpublished. Perhaps 100 individual abstracts.
    • Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. 1997. Colorado rare plant field guide. Prepared for Bureau of Land Management, U.S. Forest Service and U.S. Fish and Wildlife Service by Colorado Natural Heritage Program.
    • U.S. Fish and Wildlife Service (USFWS). 2007. Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition To List Sclerocactus brevispinus (Pariette cactus) as an Endangered or Threatened Species; Taxonomic Change From Sclerocactus glaucus to Sclerocactus brevispinus, S. glaucus, and S. wetlandicus. Federal Register 72(180): 53211-53222.
    • U.S. Fish and Wildlife Service (USFWS). 2009. Endangered and Threatened Wildlife and Plants; Taxonomic Change of Sclerocactus Glaucus to Three Separate Species. Federal Register 74(177): 47112-47117.
    • U.S. Fish and Wildlife Service. 1990. Recovery Plan for Sclerocactus glaucus.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Western Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 532 pp.

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