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Thick-leaf Bladderpod - Physaria pachyphylla

Species of Concern
Native Species

Global Rank: G2G3
State Rank: S2S3
(see State Rank Reason below)
State Threat Score: High - Medium
CCVI: Moderately Vulnerable
C-value:


Agency Status
USFWS:
USFS:
BLM: SENSITIVE


 

External Links





State Rank Reason (see State Rank above)
Physaria pachyphylla is a local endemic of the Pryor Mountain foothills and desert that crosses the Montana – Wyoming state boundary (Pipp, Heidel, and Herman 2025). Physaria pachyphylla was formally recognized as a 'new' species in 2007. Plants occupy a restricted habitat composed of dry, sparsely vegetated, and stony soil, derived from limestone and/or diatomaceous earth (Grady and O'Kane 2007). Where habitat is appropriate, plants may be abundant. Where Physaria pachyphylla and P. spatulata overlap, a few individuals of intermediate morphology have been found, suggesting that there is possible introgression between the species. Physaria pachyphylla populations are at-risk to loss from the introduction of non-native plants (Bromus tectorum and Malcolmia africana), ground disturbing activities from potential gypsum mining and related mining activities, and off-road vehicle use. A 2025 review of Physaria pachyphylla retains an S2S3 rank in Montana. Monitoring data that assesses population trends in places with and without recognized or potential threats is needed.
Thick-leaf Bladderpod (Physaria pachyphylla) Conservation Status Summary
State Rank: S2S3
Review Date = 06/12/2025
How we calculate Conservation Status

See the complete Conservation Status Report
 
General Description
PLANTS: A perennial, silvery pale-green forb with a strong basal rosette of leaves, and decumbent to ascending stems of 2-15 cm tall that usually arise from an unbranched taproot (caudex), 4-7 mm thick. Flowering stems are often well exerted beyond the basal leaves and clothed in old leaf bases. Sources: Grady and O’Kane 2007; Lesica et al. 2022; Appendix A in Pipp, Heidel, and Herman 2025

LEAVES: Basal leaves are leathery, oblanceolate to orbicular in shape, somewhat cupped, have smooth (entire) margins, are 15–50 mm long, 4-7 mm wide, and often 1 mm thick. Petioles are distinct from the blades. Stems are initially decumbent and later ascend. Stem leaves are alternately arranged and spatulate-shaped. The foliage takes on a pale green appearance due to the dense covering of silver-gray, stellate hairs (trichomes). Leaf hairs are 0.5 mm in diameter with 5 main rays, twice bifurcate (with 16-20 terminal rays), slightly fused near the bases of the main rays, and appressed close to the leaf surface. Sources: Grady and O’Kane 2007; Lesica et al. 2022; Appendix A in Pipp, Heidel, and Herman 2025

INFLORESCENCE: A raceme of pale yellow flowers, arranged in unbranched, elongated stalks, with curved, ascending pedicels of 3-10 mm long. Sepals are 4, yellow, and pale, 3.5-4 mm long. Petals are 4, yellow, and 6–8 mm long. Stamens are 6 (4 long and 2 short). Pistil is singular. Fruits are a slightly ovoid silicle. Sources: Grady and O’Kane 2007; Lesica et al. 2022; Appendix A in Pipp, Heidel, and Herman 2025

TAXONOMY & NOMENCLATURE
The genera of Physaria and Lesquerella were united under the older name of Physaria by Shehbaz and O'Kane (2002). These genera were originally separated by Rollins in his publication Cruciferae of Continental North America (1993). Rollins separated Physaria as possessing strongly didymous fruits (see Reproductive Characteristics) with deep sinuses between the valves and having fruits compressed perpendicular to the replum (Shehbaz and O'Kane 2002). Likewise, Rollins separated Lesquerella as having non-didymous fruits with shallow to no distal sinuses and having fruits compressed parallel to the replum or lacking any compression (Shehbaz and O'Kane 2002). However, the increasing amount of molecular, morphological, distributional, and ecological data do not support the distinctions put forth by Rollins (1993). Most of the members of Lesquerella now belong to the genus Physaria, except for species which possess auriculate-leaves which have been placed in the genus Paysonia (O’Kane in Flora of North America (FNA) 2010). Physaria and Lesquerella are indistinguishable in almost every morphological aspect and are monophyletic (descended from a single taxon) (Shehbaz and O'Kane 2002; O’Kane in FNA 2010). Scientific naming standards require that the oldest name be preserved; Physaria has been recognized as a genus since 1838 while Lesquerella was established in 1888 (Shehbaz and O'Kane 2002).

Physaria pachyphylla was recognized as a novel taxon in 1998, and formally described as a species new to science in 2007 by Ben Grady and Steve O'Kane.

“Physa” is Greek for 'bladder' which is in reference to the inflated fruits in some species of Physaria (O'Kane in FNA 2010). The common name of Thick-leaf Bladderpod was published by Grady and O'Kane (2007). “Pachy” means fat or thick, and “phylla” means leaves, referring to the stout or thick leaves of this species (Gledhill 1990).

Phenology
Generally, flowering from June to July (Cross 2010; O’Kane in Flora of North America (FNA) 2010). However, earlier dates are also expected and dependent upon local climate conditions.

Diagnostic Characteristics
Montana has a rich diversity of 17 bladderpod species that inlcudes 4 endemic species. A technical key and mature fruits are necessary to distinguish Physaria species. The following species occur in Carbon County and can be distinguished from Physaria pachyphylla based on a suite of characteristics found in a given population:

Thick-leaf BladderpodPhysaria pachyphylla, SOC
*Inflorescence is a subumbellate raceme.
*Fruiting pedicels curve upwards (ascend), are 3-10 mm long, and less than 2 times longer than fruit.
*Fruits inflated, narrowly elliptic to globose (not obviously appearing 2-lobed), and 3-6 mm tall. Style is 1-3 mm long, shorter than the mature fruit (silicle).
*Basal leaves have distinct petioles and blades. Basal blades are oblanceolate to orbicular in shape, nearly 1 mm thick, and cupped (not folded).
*Plants grow on white to pinkish, limestone and gypsum soils on exposed ridges and slopes in the valley zone.
*Refer to Appendix A in Pipp, Heidel, and Herman (2025).

Sharpleaf twinpod - Physaria acutifolia
*Pedicels are spreading, straight to sigmoid, 5-10 mm long.
*Fruits inflated and obviously 2-lobed, 6-10 mm wide.

Double Bladderpod - Physaria brassicoides, SOC
*Pedicels are spreading, straight or sigmoid, 5-20 mm long.
*Fruits inflated and obviously 2-lobed, 7-10 mm wide. Replum (thin wall that separates the lobes) is narrow and constricted in the middle.

Curved Bladderpod - Physaria curvipes
*Pedicels are sigmoid to speading, 4-7 mm long.
*Fruits inflated (not obviously 2-lobed), ovoid, and 5-9 mm tall. Style is less than half the length of the fruit (silicle).
*Basal leaf blades are thinner than 1 mm.

Wooly Twinpod - Physaria didymocarpa var. lanata, SOC
*Pedicels are spreading, straight to curved, 3-12 mm long.
*Fruits inflated and obviously 2-lobed, 7-20 mm tall.
*Basal Leaves obovate in shape with entire to coarsely dentate margins.

Lesica’s BladderpodPhysaria lesicii, SOC
*Pedicles are recurved in an arc, 4-11 mm long. Stems and pedicles are thread-like and flexuous (filiform).
*Fruits are globose, inflated and 2-4 mm high
*Plants are less robust with thinner leaves and caudices. Plants grow at higher elevations, relative to Thick-leaf Bladderpod.

Rocky Mountain TwinpodPhysaria saximontana var. dentata, SOC
*Pedicels are spreading to straight to curved, 5–10 mm long.
*Fruits are inflated and obviously 2-lobed, 7-11 mm high.
*Basal leaf blades are orbicular to rhombic in shape, 15–40 mm long, and deeply few-toothed or lyrate.
*Plants typically grow in limestone-derived soils of grasslands and fellfields on exposed slopes in the montane zone.

Spatula-leaf Bladderpod - Physaria spatulata
*Pedicles are sigmoid-spreading, 4-12 mm long - at least twice as long as the fruit (silicle).
*Fruits inflated, ovoid (not obviously 2-lobed), and 2-5 mm high. Style is more than half the length of the fruit.
*Basal leaf blades thinner than 1 mm.
*Plants grow in sandy or gravelly soil (calcareous or not) on exposed slopes and ridges in grasslands, steppe, woodlands, and fellfields in the plains, valleys, montane, and alpine zones.
*Refer to Appendix A in Pipp, Heidel, and Herman (2025).

Great Plains Bladderpod - Physaria arenosa
*Pedicles are recurved downward 5-10 mm long.
*Fruits are globose (not obviously 2-lobed), 3-5 mm high
*Basal leaves on the outside are oblong to narrowly ovate, not spatulate, and 1-5cm long with entire margins.

Silver Bladderpod - Physaria ludoviciana, SOC
*Pedicles are recurved downward 10-16 mm long.
*Fruits are globose (not obviously 2-lobed), 3-4 mm high
*Basal leaves are erect, linear, 3-7 cm long.

Species Range
Montana Range Range Descriptions

Native
 


Range Comments
Thick-leaf Bladderpod is a regional endemic species, occurring only in the Pryor Mountain foothills and desert that crosses the Montana-Wyoming border (Lesica et al. 2022; Pipp, Heidel, and Herman 2025). As such, it is considered by some experts to be a local endemic species (Pipp, Heidel, and Herman 2025). From 1983 to 2024, occurrences have been documented in south-central Montana and north-central Wyoming that cover a global range of about 107 square miles (277 square kilometers) between the Gypsum Creek vicinity and Bighorn River.

Thick-leaf Bladderpod was first collected by Lesica in 1983 in Carbon County, Montana. It was not recognized as a new species until after O'Kane collected another specimen in 1998 and pursued further research with graduate student Ben Grady (www.pnwherbaria.org; Grady and O'Kane 2007). Ben Grady described the new species in 1998 and along with Steve O'Kane published the findings in a 2007 paper that focused on Physaria in western North America (Grady and O'Kane 2007). A 2001 collection made in Big Horn County, Wyoming by Botanist Bonnie Heidel was later annotated by Grady and represents Wyoming's first occurrence.


Observations in Montana Natural Heritage Program Database
Number of Observations: 243

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Thick-leaf Bladderpod grows on stony, calcareous (limestone or gypsum) soils on exposed slopes and ridges in the valley zones in Carbon County, Montana (Lesica 2022). The calcareous parent material is derived from limestone or a combination of limestone and diatomaceous earth and is generally comprised of silt-sized particles, which breaks down to its finest texture or to coarse gravel (Grady and O'Kane 2007; Pipp, Heidel, and Herman 2025). In Montana and Wyoming, plants have been found in the Chugwater Formation and Gypsum Spring Formation (also called Piper Formation in Montana) (Pipp, Heidel, and Herman 2025). Plants have been found where surface soils vary in color from white to pinkish but are not red to dark red. Plants grow in exposed settings, often situated on prominent landforms such as ridge tops and rims, butte shoulders, and rocky escarpment breaks, and also at the base of slopes and on low mounds in valleys or open terrain (Pipp, Heidel, and Herman 2025). Across its global range, plants have been found at elevations ranging from 4,150 to 5,680 feet (1,265 to 1,732 meters) above sea level (Pipp, Heidel, and Herman 2025).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see here

Ecological Systems Associated with this Species

Ecology
ASSOCIATED SPECIES
In Montana and Wyoming, Thick-leaf Bladderpod occupies sparsely vegetated habitat with mainly low-growing perennial forbs and bunchgrasses (Grady and O'Kane 2007; Pipp, Heidel, and Herman 2025). Associated plant species are either consistently or occasionally present. Consistently common forb and grass associates included: Hooker's Sandwort (Arenaria hookeri), Fourwing Saltbush (Atriplex canescens), Mountain Cat’s eye (Cryptantha cana), Parasol Buckwheat (Eriogonum brevicaule var. canum), Stemless Four-nerve Daisy (Hymenoxys acaulis), Richardson's Bitterweed (Hymenoxys richardsonii), Spiny and Moss Phlox (Phlox hoodii and P. muscoides, respectively), Stemless Mock Goldenweed (Stenotus acaulis), Rayless Tansy-aster (Xanthisma grindelioides), Bluebunch Wheatgrass (Elymus spicatus), and Purple Three-Awn Grass (Aristida purpurea var. fendleriana). In the foothills, Utah Juniper (Juniperus osteosperma) was often present.

POLLINATORS
No pollinators have been documented specifically for Thick-leaf Bladderpod.Outcrossing pollination by insects is a required method of fertilization for successful reproduction of other Physaria species (Clark 2013; Claerbout et al. 2007). Insects, including ground-nesting bees, have been documented as pollinators for other Physaria species (Cross 2010; Meier et al. 2011).

Reproductive Characteristics
Plants reproduce by seed.

FLOWERS
Perfect (contain male and female organs). Sepals are pale yellow and elliptic to oblong in shape. Petals are yellow and strap-shaped (ligulate). Pistil has a 2-chambered superior ovary and a single style, 1-3 mm long.

FRUITS
The fruit is a silicle. Silicle is erect, globose or ellipsoid, slightly inflated with a slight apical constriction (slight latispetate compression), densely pubescent with closely-appressed hairs (trichomes), and 3-6 mm tall. Style is shorter than mature fruit, (2.5)1-3(4) mm long. Silicle appears 1-lobed, but is composed of two valves or chambers. Each fruit has 8 seeds, distributed in 2 chambers (4 ovules per locule).

Management
RESEARCH NATURAL AREAS and AREA OF CRITICAL ENVIRONMENTAL CONCERN PROGRAM
The Research Natural Area (RNA) program is a nationwide system created to protect a network of federally administered public lands established for the purpose of scientific research, maintaining biological diversity, and education (USFS 2014). The intent is to designate RNAs that represent the full array of North American ecosystems with their biological communities, habitats, natural phenomena, and geological and hydrological formations. These intact protected areas are managed to maintain their natural and primitive character with a minimum of human disturbance. Each RNA also serves as a baseline of ecological information that can be used to compare against other similar, yet managed ecological systems.

A type of RNA is the Area of Critical Environment Concern (ACEC). The ACEC program was established in the 1976 Federal Lands Policy and Management Act and is managed by the Bureau of Land Management (BLM) (Wikipedia Contributors 2020). Places designated as ACECs require special management to protect important historical, cultural, and scenic values, fish and wildlife, or other natural resources (BLM 2021). The BLM has extended the purpose of RNAs to that of preserving gene pools of typical and endangered plants and animals (BLM 2015; BLM 2021).

Pryor Foothills RNA/ACEC – East Pryor Mountain ACEC
The Pryor Foothills RNA/ACEC has management goals to protect unique vegetation and significant historic and cultural values. The East Pryor Mountain ACEC has management goals to protect special status plant species, wild horse and wildlife habitat, and historical, cultural, and paleontological resources. Intact populations of Thick-leaf Bladderpod live in portions of the Pryor Foothill RNA-ACEC and East Pryor Mountain ACEC. These RNAs/ACECs were established in the Approved Resource Management Plan by the Montana/Dakotas BLM (MT/Dakotas BLM), Billings Field Office in 2015 (BLM 2015). Both RNAs/ACECs were recommended by the MT/Dakotas BLM State Director for withdrawal from all locatable mineral entry, which if approved would apply to new claim applicants, and other stipulations (BLM 2015). However, recommendations listed in the 2015 Billings Field Office - Approved Resource Management Plan are still awaiting final approval by the U.S Congress (BLM 2015).

BLM SPECIAL STATUS SPECIES
The BLM Special Status Species Policy (Manual 6840) gives the State Director the responsibility to designate Bureau sensitive species for their respective jurisdictions and allows the list to be reviewed and updated at least every 5 years in coordination with State agencies responsible for fisheries, wildlife, and botanical resources and Natural Heritage Programs (MT/Dakotas BLM 2020). Further the State Director has the responsibility to implement procedures for the conservation of all special status species on BLM-administered lands within Montana, North Dakota, and South Dakota (MT/Dakotas BLM 2020).

Thick-leaf Bladderpod is designated as a Montana/Dakotas BLM Sensitive Species for the Billings Field Office (MT/Dakotas BLM 2020). The Montana/Dakotas BLM Sensitive status was given in part because it is a local endemic with historical and relatively current occurrences. It has been designated as Sensitive by the Montana/Dakotas BLM since 2014. The Montana/Dakotas BLM Special Status Species Policy for Sensitive plants provides guidance on field inventories and mitigation measures (MT/Dakotas BLM 2020).

ENDANGERED SPECIES ACT
Recognizing that America's rich natural heritage is of aesthetic, ecological, educational, recreational, and scientific values to our Nation and its people, the Endangered Species Act (ESA) was created to recover and protect imperiled species. The ESA of 1973 as amended by Congress provides for the conservation of endangered and threatened species of fish, wildlife, and plants, and for other purposes. The ESA mostly requires the U.S. Fish and Wildlife Service (USFWS) to: a) list, classify, protect, and recover species [Sections 4, 9, and 12], b) review and evaluate federal actions for potential affects to listed species [Section 7], c) oversee recovery activities [Sections 4, 5, and 6]; d) work cooperatively with the States [Section 6] and internationally [Section 8]; and e) provide exemptions (permits) for scientific efforts and conservation activities [Section 10]. The USFWS uses five main factors to determine if a proposed species warrants listing under the ESA: 1) present or threatened habitat/range loss, 2) overutilization, 3) disease/predation, 4) inadequacy of protections, and 5) other threats. The de-listing of a species is assessed using three criteria: 1) recovery, 2) extinction, or 3) erroneous information at the time of listing. The USFWS uses a Species Status Assessment to evaluate the resiliency, redundancy, and representation, to understand the current and potential future viability of a species to inform listing, consultation, and recovery decisions (USFWS 2016; USFWS Species Status Assessment).

Thick-leaf Bladderpod under the ESA
On March 11, 2021 a petition to list Thick-leaf Bladderpod and designate critical habitat under the Act was submitted to the USFWS. The 90-day Finding found substantial scientific or commercial information indicating that listing as a threatened or endangered species may be warranted (USFWS 2021). In 2023 Thick-leaf Bladderpod was put onto the National Listing Workplan. In 2024, the USFWS initiated both a 12-month review and a Species Status Assessment (SSA). The USFWS anticipates making a listing-determination in 2026.


Threats or Limiting Factors
Across its range in Wyoming and Montana, the following threats have been identified as factors that can, if not properly mitigated or managed, contribute to putting Thickleaf-Bladderpop populations at risk of state extirpation in Montana or global extinction (Montana Native Plant Society 2021; Pipp, Heidel, and Herman 2025):

Mining and Quarrying
Thick-leaf Bladderpod populations occur on soils that can or have been mined for gypsum, uranium, gravel, and other earth materials. Potential negative direct impacts include removal and trampling of plants and ground-disturbance. Potential indirect negative impacts come from ground-disturbing activities that can destroy the biological soil crust layer, expand non-native plant species, create soil erosion or compaction, and alter soil and water-holding properties; thereby, modifying the necessary habitat components for Thick-leaf Bladderpod. Soils in the Chugwater, Gypsum Spring, or Piper Formations are known to be very susceptible to erosion.

Without appropriate mitigation, the potential for ground-disturbance to known Thick-leaf Bladderpod populations come from proposed mining activities for gypsum exploration, safe-guarding abandoned defense-related uranium mines (DRUM), and possible quarrying for limestone (Pipp, Heidel, and Herman 2025). Safe-guarding DRUM sites is done to reduce radiation exposure to people and wildlife, and typically involves some access road reconstruction; installing polyurethane foam, cable nets, or bat gates across adits and shafts; or back-filling features with local materials.

Non-native Plant Species
The arid landscape in which Thick-leaf Bladderpod occurs is predominately in native, intact habitat. However, Cheatgrass (Bromus tectorum) and African mustard (Malcolmia africans) plants are found within and along the road systems for at least three Thick-leaf Bladderpod occurrences. Cheatgrass and African Mustard lack population controls and can outcompete native plants for soil, water, and nutrients. In addition, the establishment of Cheatgrass can alter the ecology and fire cycle of a site (Peters and Bunting 1994; Weber, Budel, and Belnap (eds.) 2016).

Recreation
Off-road vehicle (ORVs) use can directly trample Thick-leaf Bladderpod, resulting in death or damage. Potential indirect impacts from ORVs can create soil erosion and compaction, alter the soil's microtopography, and provide vectors for non-native plant establishment. Unauthorized ORV use has been observed at one occurrence, and is being addressed by the MT/Dakotas BLM.

Lack of Federal Protection
Portions of the Pryor Foothills RNA/ACEC and East Pryor Mountains ACEC contain intact, viable populations of Thick-leaf Bladderpod. The MT/Dakotas BLM, Approved Resource Management Plan for the Billings Field Office recommended a withdrawal from mineral entry and all locatable minerals along with other stipulations (MT/Dakotas BLM 2015). The formal approval of these recommendations would help protect the plants within these ACECs from mining activities proposed by new claim applications. The change in management recommendations put forth by the MT/Dakotas BLM requires formal approval by the U.S. Congress or the Secretary of Interior, which as of 2025, has not been granted. The lack of formally approving the 2015 recommendations contributes risk, potentially making Thick-leaf Bladderpod plants more vulnerable to loss.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Thick-leaf Bladderpod include potential negative consequences from proposed mining, quarrying, and related mining activities, non-native plant populations, unauthorized off-road vehicle use, and a lack of federal protections at specific ACECs (MTNHP Threat Assessment 2025). An overall State Threat Score of "High to Medium" is assigned because proposed actions have the potential to harm, especially without appropriate mitigation, at least some Thick-leaf Bladderpod occurrences in Montana.

References
  • Literature Cited AboveLegend:   View Online Publication
    • Al-Shahbaz, I.A. and S.L. O'Kane. 2002. Lesquerella is united with Physaria (Brassicaceae). Novon 12:319-329.
    • BLM Billings Field Office. 2015. Approved Resource Management Plan Appendices. Billings, MT: U.S. Department of the Interior Bureau of Land Management. 438 p.
    • Cavaroc, V.V. and R.M. Flores. 1991. Red beds of the Triassic Chugwater Group, Southwestern Powder River Basin, Wyoming. pp. E1-!17. IN: V.F. Nuccio, P.L. Hansley, W.A. Cobban, and C.G. Whitney, Evolution of Sedimentary Basins: Powder River Basin. Denver, CO: U.S. Geological Survey Bulletin, 1917-E.
    • Claerbout, A.E., J.M. Coons, H.R. Owen, and K.R. Robertson. 2007. Floral Biology of Physaria ludoviciana (Brassicaceae), a Plant Rare to the Midwest. Castanea 72(3):130-137.
    • Clark, S.L. 2013. Reproductive biology and impacts of energy development on Physaria congesta and Physaria obcordata (Brassicaceae), two rare and threatened plants in the Piceance Basin, Colorado. M.Sc. Thesis. Logan, UT: Utah State University. 90 p.
    • Cross, P. 2010. Bladderpod: A study in diversity. Kelseya 23(4):8-9.
    • Flora of North America Editorial Committee, eds. 2010. Flora of North America North of Mexico. Volume 7. Magnoliophyta: Salicaceae to Brassicaceae. Oxford University Press, Inc., NY. 832 pp.
    • Gledhill, D. 1990. The names of plants. 2nd Ed. New York, NY: Cambridge University Press. 426 p.
    • Grady, B. R., and S. L. O'Kane. 2007. New Species and Combinations in Physaria (Brassicaceae) from Western North America. Novon 17 (2): 182-192.
    • Heidel, B. 2016. Noteworthy collection. Madrono 63(1):7.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Meier, R., M. Joseph, M. Arduser, and E. Westhus. 2011. The pollination biology of an annual endemic herb, Physaria filiformis (Brassicaceae), in the Missouri Ozarks following controlled burns. Journal of the Torrey Botanical Society 138(3):287-297.
    • MT/Dakotas BLM. 2020. 2020 Montana/Dakotas Special Status Species List. Instruction Memorandum No. MT-2020-012. March 16th. Montana/Dakotas State Office, 2001 Southgate Drive, Billings, Montana.
    • MTNHP Threat Assessment. 2021. State Threat Score Assignment and Assessment of Reported Threats from 2006 to 2021 for State-listed Vascular Plants. Botany Program, Montana Natural Heritage Program, Helena, Montana.
    • Peters, E.F., and S.C. Bunting. 1994. Fire Conditions pre- and post-occurrence of annual grasses on the Snake River Plain. In: S.B. Monsen and S.G. Kitchen (eds.), Proc. Ecology and management of annual rangelands. USDA For. Ser. Gen. Tech. Rep. INT-GRR-313, 31-36.
    • Pipp, Andrea, Bonnie Heidel, and Kenda Herman. 2025. Physaria pachyphylla (Thick-leaf Bladderpod) in Montana and Wyoming: Field Surveys and Status Assessment, 1983-2024. January 27, 2025; revised April 14 , 2025. Report to the USDI Bureau of Land Management, Montana/Dakotas State Office, Billings, Montana and Wyoming State Office, Laramie, Wyoming. Prepared by the Montana Natural Heritage Program, Helena, Montana and Wyoming Natural Diversity Database, Laramie, Wyoming. 51 pp.
    • Rollins, R. C. 1993. The Cruciferae of Continental North America: systematics of the mustard family from the Arctic to Panama. Stanford University Press, Stanford, California. 976 pp.
    • U.S Fish and Wildlife Service (USFWS). 2016. USFWS Species Assessment Framework: An Integrated Analytical Framework for Conservation. August. Version 3.4.
    • U.S. Fish and Wildlife Service. 2021. 90-Day Finding Petition Review Form for Physaria pachyphylla. Federal Docket Number: FWS-R6-ES-2021-0117. Washington D.C.
    • USDA Forest Service. 2014. Research Natural Areas. Accessed 4 February 2021. https://www.nrs.fs.fed.us/rna/
    • USDI Bureau of Land Management. 1996. Special status species management. BLM Manual Supplement 6840 of 8 April 1996. Billings, MT.
    • USDI Bureau of Land Management. 2021. Areas of critical environmental concern. Accessed January 28, 2021. https://www.blm.gov/programs/planning-and-nepa/planning-101/special-planning-designations/acec
    • Weber, Bettina, Burkhard Budel, and Jayne Belnap (editors). 2016. Biological Soil Crusts: An Organizing Principle in Drylands. Ecological Studies, Analysis and Synthesis, Volume 226. Springer International Publishing, Switzerland.
    • Wikipedia contributors. 2020. Area of critical environmental concern. Wikipedia, The Free Encyclopedia. Accessed 27 January 2021. https://en.wikipedia.org/w/index.php?title=Area_of_Critical_Environmental_Concern&oldid=994305208
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Grady, Benjamin R. 2005. Molecules, morphology, and biogeography: an analysis of the phylogeny and taxonomy of the Physaria reediana species complex (Brassicaceae).
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Shepard, E. 2005. BLM Land Use Planning Handbook H-1601-1. Grand Junction, CO: U.S. Department of the Interior Bureau of Land Management. 161 p.
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