Montana Field Guide

PLANTS: A loosely mounded perennial herb with a rosette-like growth form, 2-15 cm tall. Flowering stems are well exerted beyond the basal leaves and clothed in old leaf bases from a simple, rarely branched taproot (caudex) 4-7 mm thick. Sources: Grady and O’Kane 2007; Lesica et al. 2012.

LEAVES: Basal leaves are oblanceolate to orbicular, 15–50 mm long by 4-7 mm wide, distinct from the petioles, entire, and somewhat cupped. Stems are first decumbent and later ascend to 2–15 cm tall with alternate, spatulate-shaped leaves. The foliage takes on a pale green appearance due to the dense covering of silver-gray, 5-rayed, stellate hairs (trichomes). The 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. 2012.

INFLORESCENCE: Flowers are arranged on an unbranched, elongated stalk and have curved, ascending pedicels (racemose inflorescence) which are 3-10 mm long. Flowers have 4 pale yellow sepals (3.5-4 mm), 4 separate yellow petals (6–8 mm), 6 stamens (4 long and 2 short), and 1 pistil. Fruits are silicles. Sources: Grady and O’Kane 2007; Lesica et al. 2012.

“Physa” means bladder referring to the inflated fruits in some species of this genus. “Pachy” means fat or thick, and “phylla” means leaves, referring to the stout or thick leaves of this species (Gledhill 1990).

Flowering June to July (Cross 2010; O’Kane in Flora of North America (FNA) 2010).

Montana has a rich diversity of bladderpod species totaling 17, of which 4 are endemic including Thick-leaf Bladderpod. The following Physaria species occur in Carbon County and can be distinguished from Physaria pachyphylla based on these characteristics:

Thick-leaf Bladderpod – Physaria pachyphylla, SOC
*Pedicels curve upwards (ascend), 3-10 mm long.
*Fruits inflated, not 2-lobed, and narrowly elliptic to ovoid, 3-6 mm tall. Style is more than half the length of the fruit (silicle).
*Basal leaves have distinct petioles and blades. Blades are spatulate to oblanceolate in shape, nearly 1 mm thick and cupped (but not folded), and with entire margins [key characteristic].
*Plants grow on pinkish or reddish soils derived from limestone on exposed slopes and ridges in valleys.

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

Double Bladderpod - Physaria brassicoides, SOC
*Pedicels are spreading, straight, or sigmoid, 5-20 mm long.
*Fruits inflated and 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 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, or sigmoid, 3-12 mm long.
*Fruits inflated and 2-lobed, 7-20 mm tall.
*Basal Leaves obovate in shape with entire to coarsely dentate margins.

Lesica’s Bladderpod – Physaria 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, elative to Thick-leaf Bladderpod.

Rocky Mountain Twinpod – Physaria saximontana var. dentata, SOC
*Pedicels are spreading to straight to curved, 5–10 mm long.
*Fruits are inflated and 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, not 2-lobed, ovoid, 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.

Great Plains Bladderpod - Physaria arenosa
*Pedicles are recurved downward 5-10 mm long.
*Fruits are globose not 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 2-lobed, 3-4 mm high
*Basal leaves are erect, linear, 3-7 mm long.

TAXONOMY
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 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 requires 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).

In Montana, Thick-leaf Bladderpod grows in dry, barren, and stony, yet edaphically diverse soils in the Pryor Mountain Desert which occur on exposed slopes, ridges, and valleys (Grady and O’Kane 2007; O’Kane in FNA 2010; and Lesica et al. 2012). The species is apparently limited to pinkish or reddish soils derived from limestone or a combination of limestone and diatomaceous earth at elevations ranging from 1,300 to 1,600 meters above sea level (Grady and O’Kane 2007; Lesica et al. 2012).

In Wyoming, it is associated with outcrops in the Chugwater Formation (Heidel 2016) which consists mainly of siltstones and shales with interspersed sandstones. The formation is brick-red in color, caused by the oxidation of iron minerals in the rock (Cavaroc and Flores 1991).

ASSOCIATED SPECIES
In Montana, Thick-leaf Bladderpod can be found growing with other mat forming perennials, though vegetation is often sparsely distributed. Associated forb and grass species include saltbush (Atriplex), buckwheat (Eriogonum), phlox (Phlox), cat’s eye (Cryptantha), vetch (Astragalus), rock goldenrod (Petradoria), needlegrass (Stipa), and wheatgrass (Elymus) (Grady and O’Kane 2007). Concomitant woody species include Limber Pine (Pinus flexilis), Utah Juniper (Juniperus osteosperma), and Curl-leaf Mountain Mohagany (Cercocarpus ledifolius) (Grady and O’Kane 2007). In Wyoming, it is associated with Rubber Rabbitbrush (Chrysothamnus nauseosus var. graveolens (syn. Ericameria nauseosus ssp. graveolens)) and Badlands Mule-ears (Wyethia scabra) (Heidel 2016).

POLLINATORS
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, P. 2010; Meier et al. 2011). No pollinators have been documented specifically for Thick-leaf Bladderpod.

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-celled superior ovary and a single style, 1-3 mm long.

FRUITS
The fruit is a silicle, 2.5-4.0 mm long. The silicle is erect, inflated, narrowly elliptic to ovoid or lance shaped, 3–6 mm high by 3-4 mm wide, and tipped with a style that at least half the length of the mature fruit. Each fruit has 8 seeds, distributed in 2 chambers (4 seeds per locule).

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 Foothill RNA/ACEC
This RNA-ACEC was established in the Approved Resource Management Plan by the MT/Dakotas BLM, Billings Field Office, recommended for approval by the MT/Dakotas BLM State Director in 2015, and is awaiting final approval by the U.S Congress (BLM 2015). The RNA-ACEC is approximately 2,606 acres in size. The management goals for the Pryor Foothills RNA/ACEC are to protect a large concentration of BLM's special status plant species and rare plant communities (unique vegetation) and to protect significant historic and cultural values in the Gyp Springs area. Large, intact populations of Thick-leaf Bladderpod live in the Pryor Foothill RNA-ACEC. A scattering of populations occur in vicinity of the Pryor Foothill RNA-ACEC. See Range Comments.

BLM SPECIAL STATUS SPECIES
The BLM Special Status Species Policy (Manual 6840) gives the State Director the responsibilities 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).

Across its range in Wyoming and Montana, current and potential long-term threats to Thick-leaf Bladderpod include (Montana Native Plant Society 2021):

Gypsum Mining: Gypsum is a common mineral found in the Chugwater Formation. Gypsum claims have been made on public lands in vicinity of Thick-leaf Bladderpod. Potential negative impacts from mining activities include direct removal and trampling of plants. Potential indirect negative impacts from mining activities include disturbance to habitat from soil erosion, soil compaction, and colonization by invasive species. Soils in the Chugwater Formation are known to be very susceptible to erosion.

Invasive 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) are known to occur along roads that are near to thick-leaf Bladderpod populations. There is the potential for negative impacts based on the assumption that these exotics would be more competitive for soil water and nutrient resources.

Recreation: Off-road vehicle (ORVs) use commonly occurs further north in the Pryor Mountains. It is suspected that at least some ORV use could occur in vicinity of the Thick-leaf Bladderpod. Potential negative impacts from ORVs could include direct impacts to the plant from trampling and indirect impacts from soil erosion, soil compaction, and colonization of the habitat by invasive species.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Thick-leaf Bladderpod include potential consequences from proposed oil and gas exploration and expansion of non-native plant populations (MTNHP Threat Assessment 2021). Road construction and drill site activity proposed in the Pryor Foothill RNA would create ground disturbance in an area where soils are prone to rapid erosion. Indirectly, this ground disturbance could remove biotic soil crusts, which contribute to the stability of surface soils, and requires years or decades recover. Nearby non-native plants may outcompete Thick-leaf Bladderpod and have a strong potential to increase where ground disturbance exposes bare soil.