Physaria obcordata
Author: Rollins

Piceance twinpod

Brassicaceae (Mustard Family)

Close up of Physaria obcordata by Peggy Lyon
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Close up of Physaria obcordata by Lisa Foy
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Close up of Physaria obcordata by Jill Handwerk
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Close up of Physaria obcordata by Jill Handwerk
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Ranks and Status

Global rank: G1G2
State rank: S1S2
Federal protection status: USFWS Threatened
State protection status: None

[+] Description and Phenology

Physaria obcordata by Suzanne Wuerthele
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General description: Yellow flowered perennial herb with a stout taproot, about 10-20 cm in height. Rosette leaves are oblanceolate, the margins entire to shallowly sinuate-dentate; cauline leaves are narrowly lanceolate, the margins entire. Entire plant is covered with circular trichomes resembling solder splatters. Fruit are obcordate at maturity (Spackman et al. 1997; Ackerfield 2015).

Look Alikes: Physaria acutifolia and P. parviflora have oval/orbicular fruits (Spackman et al. 1997). 

Phenology: Vegetative growth likely begins in early May, flowering occurs from mid May through mid June. Fruit maturation through the end of July. Dehisence is from mid June through August (O'Kane 1987).

[+] Habitat

Habitat of Physaria obcordata by Peggy Lyon
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Habitat of Physaria obcordata by Susan Spackman Panjabi
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Barren white outcrops and steep slopes exposed by creek downcutting. Restricted to the Parachute Creek Member of the oil shale bearing Green River Formation (Spackman et al. 1997).

Elevation Range: 5,935 - 7,559 feet (1,809 - 2,304 meters)

[+] Distribution

Distribution of Physaria obcordata in Colorado.
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Colorado endemic: Yes
Global range: Endemic to Colorado; known from Rio Blanco County only along the Piceance and Yellow Creek drainages and at Clamity Ridge. Estimated range is 574 square kilometers, calculated in GIS by the Colorado Natural Heritage Program in 2008 by drawing a minimum convex polygon around the known occurrences.

[+] Threats and Management Issues

Summary results of an analysis of the status of Physaria obcordata based on several ranking factors. This species was concluded to be "weakly conserved”. From Rondeau et al. 2011.
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Oil and gas development is the primary threat. Mining of oil shale and/or nahcolite solution could impact up to 100% of the occupied habitat. A new nahcolite plant at Yankee Gulch, across from Dudley Bluffs was built in 2000. The lease may extend into Ryan Gulch. Additionally, a new drill pad was observed near Dudley Bluffs in 2000 (CNAP 2000). Other threats include livestock grazing and trampling by wild horses. ORV's can cause severe damage if access is allowed into Physaria obcordata habitat.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Anderson, J. 1992 c. Draft Recovery Plan for Physaria obcordata and Lesquerella congesta. Unpublished report prepared for the U.S. Fish and Wildlife Service, Grand Junction, Colorado.
    • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 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.
    • 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.
    • O'Kane, S.L. 1987. Status report for Physaria obcordata. Unpublished report prepared for the Colorado Natural Areas Program, Denver, CO.
    • Roberts, R. 1990. White River RMP/EIS Management Situation Analysis, Resource Area Profile.
    • 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.
    • Rollins, R.C. 1983. Studies in the Cruciferae of western North America. J. Arnold Arboretum 64(4): 491-501.
    • Rollins, R.C. 1993. The Cruciferae of continental North America: Systematics of the mustard family from the Arctic to Panama. Stanford Univ. Press, Stanford, California. 976 pp.
    • 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. 1990. Endangered and threatened wildlife and plants: final rule to determine Lesquerella congesta and Physaria obcordata to be threatened species.
    • U.S. Fish and Wildlife Service. 1993. Dudley Bluffs bladderpod and Dudley Bluffs twinpod recovery plan. Denver, Colorado.
    • 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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