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Snake River goldenweed (Pyrrocoma radiata)

Pyrrocoma radiata flowers
Pyrrocoma radiata plant
Pyrrocoma radiata habitat
Flowers (left), habit (center), and habitat (right) of Snake River goldenweed. Photos by ODA staff (left and center) and Rebecca Currin (right). If downloading images from this website, please credit the photographer.


Taxonomic notes
Synonym: Haplopappus radiatus

Plant description
Snake River goldenweed is a perennial species with one to several stems 30-100 cm tall arising from a woody taproot. The plant is essentially glabrous throughout. Basal leaves are tufted, broadly elliptic, usually 15-50 cm long (including the petiole) and 5-20 cm wide. The numerous cauline leaves are sharply toothed and reduced, becoming sessile above, the lower leaves obovate, the upper ovate with a clasping base. Flowering heads are 2.5-4 cm wide and number 1-12, usually in an open corymbiform arrangement, the involucres approximately 2.5 cm high, with ovate-oblong, pale-margined loose bracts. Ray and disk florets are yellow, the ray florets 0.6-1.2 cm long and numbering 17-50, the disk corollas approximately 1.5 cm long, disk florets numbering 80-100 or more. The achenes are elongate with 40-60 rigid, unequal brownish pappus bristles.

Distinguishing characteristics
Snake River goldenweed is most closely related to Pyrrocoma carthamoides, which also occurs in the Snake River canyon. Snake River goldenweed is distinguished from this more widespread congener by glabrous stems and much wider basal leaves (5-20 cm wide versus 0.5-4 cm in P. carthamoides).

When to survey
Surveys should be completed when Snake River goldenweed is flowering, from June through July. On rare occasions, flowering has been observed as late as September.

Snake River goldenweed inhabits dry, rocky, open soil with little other perennial vegetation. It typically occurs on south- to west-facing hillsides with gentle to steep slopes at elevations ranging from 610-1830 m (2000-6000 ft). It is found in slightly to very calcareous soils often overlaying a shale formation, usually in grazing-modified sagebrush/grassland communities.
Commonly associated species include Achillea millefolium, Agropyron spicatum, Amsinckia tessellata, Artemisia tridentata, Astragalus cusickii, A. purshii, Balsamorhiza sagittata, Bromus tectorum, Cardaria draba, Collomia linearis, Crepis occidentalis, Elymus cinereus, Ericameria nauseosa var. speciosa, E. viscidiflora, Erigeron pumilus, Eriogonum spp., Erodium cicutarium, Gutierrezia sarothrae, Helianthus annuus, Mentzelia laevicaulis, Penstemon speciosus, Poa sandbergii, Purshia tridentata, Sisymbrium altissimum, Sitanion hystrix, Sphaeralcea munroana, Taeniatherum caput-madusae, and Tetradymia canescens.

Snake River goldenweed is a narrow endemic restricted to the lower Snake River Canyon and adjacent slopes in eastern Oregon and adjoining Idaho, within an area less than 48 x 64 kilometers (30 x 40 miles). It occurs in the Blue Mountains and Snake River Plain ecoregions.

Oregon counties
Baker, Malheur

Federal status
Species of Concern

Livestock grazing has been shown to negatively impact reproduction and population growth rate in Snake River goldenweed populations. Documented seed predation by insects and widespread herbivory by grasshoppers in particular have also had serious negative effects on this species. Competition from annual exotic weeds introduced by livestock grazing in Snake River goldenweed habitat poses an additional threat.

Did you know?
Snake River goldenweed was described by Nuttall in 1840 based on a type specimen believed to have been collected along the Snake River near Huntington, Oregon.

Bogler, D. J. 2006. Pyrrocoma. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford. Vol. 20, pp. 413-424. Available at http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=127795. Accessed September 20, 2010.
Hitchcock, C. L., A. Cronquist, M. Ownbey, and J. W. Thompson. 1955. Vascular plants of the Pacific Northwest. Part 5: Compositae. University of Washington Press, Seattle.
Kaye, T. N. 2002. Effects of cattle grazing, insect interactions and population ecology of Snake River goldenweed (Haplopappus radiatus). Unpublished report for Bureau of Land Management, Vale District. Institute for Applied Ecology, Corvallis, Oregon.
Meinke, R.J. 1982. Threatened and endangered vascular plants of Oregon: An illustrated guide. Unpublished report for the U.S. Fish and Wildlife Service, Region 1, Portland, Oregon. Oregon Department of Agriculture, Salem, Oregon.
OFP (Oregon Flora Project). 2010. Oregon Plant Atlas. http://www.oregonflora.org/atlas.php. Accessed September 21, 2010.
ORBIC (Oregon Biodiversity Information Center). 2010a. Rare, threatened and endangered species of Oregon. Institute for Natural Resources, Portland State University, Portland, Oregon.
105 pp. Available at http://orbic.pdx.edu/documents/2010-rte-book.pdf (pdf document, 971 kB). Accessed December 13, 2010.
ORBIC (Oregon Biodiversity Information Center). 2010b. ORBIC element occurrence database. Portland, Oregon.