General description: Perennials with dense racemes of yellow flowers and basal leaves that form a strong rosette.  Plants rise from a simple caudex that is densely (silvery) pubescent.  The stems are simple from the base of the plants, decumbent to nearly prostrate, and 0.5-1.3 dm long. Basal leaf blades are broadly obovate, with shallowly dentate margins. Cauline leaves are oblanceolate to broadly obovate, 1-2.5 cm, with entire margins. Fruits are arranged in pairs (hence the common name twinpod).  The fruit pods are slightly flattened (contrary to replum) to uncompressed, 4-9 × 2-8 mm, and the apical and basal sinuses are narrow and deep.

Look Alikes: Physaria vitulifera has larger, fiddle shaped leaves, and the constriction separating the locules of the fruit is much deeper above than below. The basal leaf margins on P. bellii are not incised, while they are deeply and broadly incised on P. vitulifera. The hybrid species, P. vitulifera x bellii found in Jefferson County, has incised leaves and wrinkly fruits (Ackerfield 2012, Smith et al. 2011).

Phenology: Flowers May through June, fruits July and August (Colorado Natural Heritage Program 2012).

Physaria bellii is found along the Front Range foothills often in shale and limestone soils of the Fountain/Ingleside, Lykins, Niobrara, and Pierre formations. This species is found in association with grassland and shrubland habitats, in rocky areas and road cuts.  Commonly associated taxa include: Cercocarpus montanus, Oryzopsis hymenoides, Gutierrezia sarothrae, Rhus trilobata, Lesquerella ludoviciana, Heterostipa neomexicana. Penstemon secundiflorus, Eriogonum brevicaule, Opuntia, Dalea,Yucca, Sphaeralcea, and Heterotheca (Flora of North America 2010, Colorado Natural Heritage Program 2013).

Elevation Range: 5,089 - 6,552 feet (1,551 - 1,997 meters)

Colorado endemic: Yes
Global range: Endemic to Colorado; known from Boulder and Larimer counties. Restricted to Niobrara and Pierre Shale Formations.

The primary threat is from residential development along the Front Range of Colorado. Additional potential threats are limestone mining operations, and road construction and maintenance. Invasion of habitat by noxious weeds such as cheatgrass, smooth brome, and diffuse knapweed, may also be a threat to some occurrences. Many occurrences have been destroyed or degraded by limestone mining and housing subdivisions, however, the largest and highest quality occurrences are still viable.