Physaria bellii
Author: Mulligan

Bell's twinpod

Brassicaceae (Mustard Family)

Close up of Physaria bellii by Pam Smith
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Close up of Physaria bellii by Georgia Doyle
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Close up of Physaria bellii by Steve O'Kane
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Ranks and Status

Global rank: G2G3
State rank: S2S3
Federal protection status: None
State protection status: None

[+] Description and Phenology

Physaria bellii by Constance Sayas
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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).

[+] Habitat

Habitat of Physaria bellii by Pam Smith
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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)

[+] Distribution

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

[+] Threats and Management Issues

Summary results of an analysis of the status of Physaria bellii based on several ranking factors. This species was concluded to be “weakly conserved”. From Rondeau et al. 2011.
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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.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 pp.
    • Flora of North America Editorial Committee. 2010. Flora of North America North of Mexico. Vol. 7. Magnoliophyta: Salicaceae to Brassicaceae. Oxford University Press, New York. xxii + 797 pp.
    • Jennings, W. 1989. Final Report Colorado Natural History Small Grants Program. Prepared for The Nature Conservancy.
    • 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.
    • Kothera, L., S. M. Ward, and S. E. Carney. 2007. Assessing the threat from hybridization to the rare endemic Physaria bellii Mulligan (Brassicaceae). Biological Conservation 140: 110-118.
    • Mulligan, G.A. 1966. Two new species of Physaria in Colorado. Canadian Journal of Botany, vol. 44, pp. 1661-1665.
    • 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.
    • Peterson, J. S. and W. Harmon. 1981. Status report for Physaria bellii. 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 Univ. Press, Stanford, California. 976 pp.
    • Smith, P., S. Panjabi, J. Sovell, and S. Kuesner. 2011. CNHP field surveys of Jefferson County.
    • 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.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

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