Physaria obcordata
Rollins
Piceance Twinpod
G2ImperiledGlobal Rank
HighThreat Impact
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.145962
Element CodePDBRA220H0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderCapparales
FamilyBrassicaceae
GenusPhysaria
Other Common Names
Dudley Bluffs Twinpod (EN) Dudley Bluffs twinpod (EN)
Concept Reference
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.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2026-04-13
Change Date2026-04-13
Edition Date2026-04-13
Edition AuthorsK. Maybury and S. Spackman, rev. CNHP (2003), rev. K. Neuhaus, J. Handwerk, and S. Spackman Panjabi (2006); rev. J. Handwerk, J. (2011, 2012, 2022), Smith, J.P. (2026); Doyle, G. (2026)
Threat ImpactHigh
Range Extent250-1000 square km (about 100-400 square miles)
Number of Occurrences6 - 20
Rank Reasons
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 obcordata long term survival.
Range Extent Comments
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 709 square kilometers was calculated in GeoCAT using occurrence data provided by the Colorado Natural Heritage Program (2026).
Occurrences Comments
As of 2026 there are 12 known occurrences documented in the Colorado Natural Heritage Program database. All of the occurrences have been observed within the last 20 years. In addition, there is one possibly extirpated occurrence that was last observed in 2000.
Threat Impact Comments
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).
Ecology & Habitat
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).
Habitat
This species grows on barren white outcrops, fine chiprock, shaley hillsides, and steep slopes exposed by creek downcutting, where it is restricted to the Parachute Creek Member of the oil shale bearing Green River Formation (Spackman et al. 1997, FNA 2010).
Reproduction
This species flowers from May to June (FNA 2010).
Terrestrial Habitats
BarrensBare rock/talus/scree
Other Nations (1)
United StatesN2
| Province | Rank | Native |
|---|---|---|
| Colorado | S2 | Yes |
Threat Assessments
| Threat | Scope | Severity | Timing |
|---|---|---|---|
| 2 - Agriculture & aquaculture | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 2.3 - Livestock farming & ranching | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 3 - Energy production & mining | Restricted (11-30%) | Moderate - slight | High - moderate |
| 3.1 - Oil & gas drilling | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 3.2 - Mining & quarrying | Small (1-10%) | Unknown | High (continuing) |
| 4 - Transportation & service corridors | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 4.1 - Roads & railroads | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 8 - Invasive & other problematic species, genes & diseases | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 8.1 - Invasive non-native/alien species/diseases | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 8.1.2 - Named species | Restricted (11-30%) | Moderate - slight | High (continuing) |
| 11 - Climate change & severe weather | Pervasive (71-100%) | Serious - moderate | High (continuing) |
| 11.2 - Droughts | Pervasive (71-100%) | Serious - moderate | High (continuing) |
Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)Yes
Roadless Areas (1)
South Dakota (1)
| Area | Forest | Acres |
|---|---|---|
| Indian Creek | Buffalo Gap National Grassland | 24,666 |
References (21)
- Ackerfield, J. 2015. Flora of Colorado. Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.
- 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.
- Colorado Natural Heritage Program (CNHP). 2026. Biodiversity Tracking and Conservation System (Biotics 5). Colorado Natural Heritage Program, Colorado State University, Fort Collins.
- 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. Spackman-Panjabi. 2015. Colorado Wildlife Action Plan: 2015 Rare Plant Addendum. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado, USA.
- 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.
- 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. 2023. Dudley Bluffs bladderpod and twinpod (<i>Physaria congesta </i>and <i>Physaria obcordata</i>) Population Trend Monitoring Summary. Bureau of Land Management unpublished report.
- Krening, P. 2025. BLM – Colorado 2025 Special Status Plant Species Population Trend Monitoring Report, Colorado State Office, Denver Federal Center, Lakewood, CO.
- O'Kane, S.L. 1987. Status report for <i>Physaria obcordata</i>. Unpublished report prepared for the Colorado Natural Areas Program, Denver, CO.
- Roberts, R. 1990. White River RMP/EIS Management Situation Analysis, Resource Area Profile.
- Rollins, R.C. 1983. Studies in the Cruciferae of western North America. J. Arnold Arboretum 64(4): 491-501.
- Rollins, R.C. 1993a. The Cruciferae of continental North America: Systematics of the mustard family from the Arctic to Panama. Stanford Univ. Press, Stanford, California. 976 pp.
- 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.
- U.S. Fish and Wildlife Service (USFWS). 1990. Endangered and threatened wildlife and plants: final rule to determine <i>Lesquerella congesta</i> and <i>Physaria obcordata</i> 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. Dudley Bluffs bladderpod (Physaria (Lesquerella) congesta) and Dudley Bluffs twinpod (Physaria obcordata), 5-year review. Western Colorado Ecological Services Field Office, Grand Junction, Colorado. https://ecos.fws.gov/docs/five_year_review/doc6424.pdf