Nuttallia densa
Author: Greene

Arkansas Canyon stickleaf

Loasaceae (Blazingstar Family)

Close up of Nuttallia densa by Susan Spackman Panjabi
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Close up of Nuttallia densa by Bill Jennings
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Taxonomic Comments

=Mentzelia densa

Ranks and Status

Global rank: G2
State rank: S2
Federal protection status: BLM Sensitive
State protection status: None

[+] Description and Phenology

Nuttallia densa by Marjorie Joy. Please also see 1997 profile.
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General description: Mentzelia densa is a small perennial subshrub, usually less than 3 dm. tall. The stems branch from the base, giving the plant a hemispherical shape. The branches are white, curve upward and are covered with stiff hairs. The narrow leaves are also covered with stiff hairs. Bright yellow flowers occur singly or in threes at the ends of the branches, and open in the late afternoon. Flowers are about 2 cm. wide. The petals are narrow, widest at the middle, and pointed at the end. The fruit is oblong, 1.3 to 2 cm. long, 1 cm. in diameter and bears teeth that are about half as long as the fruit. Seeds are flattened and are surrounded by a thin, winglike membrane (Coles 1990).

Look Alikes: Distinguished from other Mentzelia species by its growth form and the presence of the previous years dried stems (Spackman et al. 1997).

Phenology: Flowering occurs in July through early August; fruit are produced in September (Spackman et al. 1997). The flowers are only open from late afternoon (around 6 p.m.) until dark.

[+] Habitat

Habitat of Nuttallia densa by Susan Spackman Panjabi
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Habitat of Nuttallia densa by Stephanie Neid
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Mentzelia densa occupies dry open areas in washes, roadsides, naturally disturbed sites, and steep rocky slopes. Plants grow in gravel, scree, or on cliffs formed from Precambrian granodiorite and gneiss. The species occurs in pinyon-juniper woodland and lower montane shrubland communities with a poorly developed understory and an open canopy. It may dominate in very open, disturbed sites such as sandy washes. It occurs as scattered individuals generally occupying 5% or less of the total vegetative canopy. The associated species are Pinus edulis, Juniperus monosperma, Juniperus scopulorum, Symphoricarpos oreophilus, Cercocarpus montanus, Artemisia tridentata, Eriogonum jamesii, Oryzopsis humenoides, Oryzopsis micrantha, Mentzelia multiflora var. leucopetala, Bouteloua gracilis, Rhus trilobata, Heterotheca villosa, Cylindropuntia inbricata, and Opuntia phaeacantha (Coles 1990).

Elevation Range: 5,400 - 7,684 feet (1,646 - 2,342 meters)

[+] Distribution

Distribution of Nuttallia densa in Colorado.
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Colorado endemic: Yes
Global range: Endemic to Colorado; known from Fremont County, and adjacent Chaffee County.  Estimated range is 2,545 square kilometers (982 square miles), calculated in GIS by drawing a minimum convex polygon around the known occurrences (calculated by the Colorado Natural Heritage Program in 2008).

[+] Threats and Management Issues

Summary results of an analysis of the status of Nuttallia densa based on several ranking factors. This species was concluded to be “moderately conserved”. From Rondeau et al. 2011.
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Recreational use is considered to be the primary threat to the species at this time (Rondeau et al. 2011). Plants are restricted to the Arkansas River Valley and threats in the area are high (general area is being developed at a rapid rate, recreational development including ORV use, and highway construction and maintenance). Recreational use of the area is expected to increase. Plants are restricted to specific habitats within a small area.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Coles, J. 1990. Status report for Mentzalia densa. Unpublished report prepared for the Colorado Natural Areas Program, Denver, CO.
    • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 pp.
    • 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.
    • 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.
    • Rondeau, R., K. Decker, J. Handwerk, J. Siemers, L. Grunau, and C. Pague. 2011. The state of Colorado's biodiversity 2011. Prepared for The Nature Conservancy. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
    • 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.
    • 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, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

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