Scientific Name : Physaria obcordata
Author : Rollins
NatureServe Explorer
Common Name : Piceance Twinpod
Current Research Activities
1997 profile
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Taxonomy
Brassicaceae (mustard family)
Ranks and Status
State Rank : S1S2
State Rank Reason : Physaria obcordata is a narrow endemic of oil shale barrens in the Piceance Basin of northwestern Colorado, USA. Of the 12 documented occurrences, many occur along roadsides where they are threatened by road maintenance and competition from non-native species. Livestock grazing and trampling by wild horses have been observed at several occurrences and oil and gas development is widespread throughout its range. Prolonged drought and increased temperatures resulting from climate change are also a threat to Physaria congesta's long term survival.
U.S. Endangered Species Act : ESA Threatened
Colorado Threatened and Endangered List : none
Other Statuses : SWAP Tier 1
Description and Phenology
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).
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Habitat
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). Associated plant species include Atriplex sp., Astragalus lutosus, Oryzopsis hymenoides, Eriogonum sp., Mentzelia sp., Cirsium sp., and Macaeranthera sp. (Anderson 1992).
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Elevation Range:
5,945 - 7,709 feet (1,812 - 2,350 meters)
Distribution
Colorado Endemic:
Yes
Range:
Physaria obcordata is endemic to Colorado, USA; known from Rio Blanco County along the Piceance, Hays and Yellow Creek drainages and at Calamity Ridge. Estimated range extent in Colorado of 711 square kilometers was calculated in GeoCAT using occurrence data provided by the Colorado Natural Heritage Program (2022).
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Threats and Management Issues
Disturbance due to mining and oil and gas development and related actions are considered to be the primary threats to the species (Rondeau et al. 2011, USFWS 2020a). Mining of oil shale and/or nahcolite solution could impact up to 100% of the occupied habitat. A nahcolite plant was built in 2000 within the species range. Nearly half of the occurrences report invasive non-native plants within the occurrences, primarily cheatgrass (CNHP 2022). Other threats include road maintenance, livestock grazing and trampling by wild horses (USFWS 2020b). ORV's can cause severe damage if access is allowed into the habitat. This species is considered to have moderate adaptive capacity and is expected to be moderately to highly vulnerable to climate change under both RCP 4.5 and 8.5 scenarios, as assessed for the 2025 Colorado State Wildlife Action Plan (CNHP 2025).
 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. |
References
- Ackerfield, J. 2015. Flora of Colorado. BRIT Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 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.
- Colorado Natural Heritage Program (CNHP). 2022. Biodiversity Tracking and Conservation System (Biotics 5). Colorado Natural Heritage Program, Colorado State University, Fort Collins.
- Colorado Natural Heritage Program (CNHP). 2025. Climate Change Vulnerability Assessment of Colorado Tier 1 and Tier 2 Plant Species of Greatest Conservation Need (SCGN) for the 2025 Colorado State Wildlife Action Plan. Colorado Natural Heritage Program, Colorado State University, Fort Collins.
- 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.
- Flora of North America Editorial Committee (FNA). 2010. Flora of North America north of Mexico. Vol. 7. Magnoliophyta: Salicaceae to Brassicaceae. Oxford University Press, New York. xxii + 797 pp.
- Handwerk, J., L. Grunau, and S. Panjabi. 2015. Colorado Wildlife Action Plan: 2015 Rare Plant Addendum. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado, USA.
- Krening, P. 2021. Dudley Bluffs bladderpod and twinpod (Physaria congesta and Physaria obcordata) Population trend monitoring summary – 2021. Prepared for the Colorado State Office - Bureau of Land Management, U.S. Department of the Interior.
- Krening, P. 2022. Dudley Bluffs bladderpod and twinpod (Physaria congesta and Physaria obcordata) Population trend monitoring summary – 2022. Prepared for the Colorado State Office - Bureau of Land Management, U.S. Department of the Interior.
- Krening, P. 2023. Dudley Bluffs bladderpod and twinpod (Physaria congesta and Physaria obcordata) Population Trend Monitoring Summary. Bureau of Land Management unpublished report.
- 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.
- 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. 1993. The Cruciferae of Continental North America:Systematics of the Mustard Family from the Arctic to Panama. Stanford University Press. Stanford, CA.
- 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.
- Tepedino, V.J. 2009. The pollination biology of a Piceance Basin endemic, Physaria obcordata (Cruciferae). Report prepared for Colorado Natural Areas Program, Denver, CO. May 18, 2009.
- Tepedino, V.J., W.R. Bowllin and T.L. Griswold. 2012. Pollinators complicate conservation of an endemic plant: Physaria obcordata (Cruciferae) in the Piceance Basin, Colorado. Natural Areas Journal, 32(2):140-148. 2012.
- U.S. Fish and Wildlife Service (USFWS). 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 (USFWS). 1993. Dudley Bluffs bladderpod and Dudley Bluffs twinpod recovery plan. Denver, Colorado.
- U.S. Fish and Wildlife Service (USFWS). 2020a. Final Recovery plan for the Dudley Bluff Bladderpod (Physaria congesta) and Dudley Bluffs Twinpod (Physaria obcordata). March 2020. U.S. Fish and Wildlife Service, Western Colorado Ecological Services Field Office Grand Junction, Colorado. Online. Available: https://ecos.fws.gov/docs/recovery_plan/Dudley%20Bluffs_Final%20RP_signed_1.pdf (Accessed 2022).
- U.S. Fish and Wildlife Service (USFWS). 2020b. 5-YEAR REVIEW Dudley Bluffs bladderpod (Physaria (Lesquerella) congesta) and Dudley Bluffs twinpod (Physaria obcordata) Western Colorado Ecological Services Field Office, Grand Junction, Colorado. https://ecos.fws.gov/docs/five_year_review/doc6424.pdf
- USDA, NRCS. 2022. 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.
