Synonyms: Eriogonum capistratum, E. capistratum var. muhlickii, E. capistratum var. welshii, E. meledonum, E ochrocephalum var. alexanderae, E. verrucosum
Crosby’s buckwheat is a low, matted perennial 0.5-15 (-20) cm tall by (1-) 10-30 cm in diameter, growing from a woody caudex with matted stems. Stems bear persistent leaf bases and reach up to 1/5 the height of the plant. Leaves are basal and arranged in tight terminal clusters, the petiole 0.2-3 (-3.5) cm long and tomentose, occasionally glandular, the blade oblanceolate to spatulate or elliptic to obovate or ovate, (0.5-) 1-2 (-3) cm long by 0.2-1 (-1.5) cm wide, and densely white- or grayish-tomentose on both surfaces, sometimes less so and greenish white adaxially. Inflorescences are capitate, 0.7-1.5 cm wide, subtended by three scalelike narrowly triangular to triangular bracts 1-3 mm long, and borne on weakly erect to erect, slender scapelike stems, floccose to tomentose or glabrous, sometimes only or also sparsely to densely glandular. Involucres number (3-) 5-8 per cluster, are turbinate to campanulate, (1.5-) 2-5 (-5.5) mm by 2-4 (-4.5) mm, rigid or membranous, tomentose to floccose, occasionally glabrous except for floccose teeth, or rarely sparsely pilose and glandular, with 5-7 teeth 0.5-1.5 mm long, erect to spreading or reflexed. Flowers are yellow to pale yellow (rarely cream), 1.5-3.5 (-4) mm, glabrous or sometimes minutely glandular (some pustulose), tepals oblong to oblong-ovate and 1/4-1/3 connate at the base, stamens 1.5-4 mm long and exserted, filaments glabrous or sparsely pilose at the base. Achenes are light brown, 2-4 mm long, and glabrous or occasionally with minute bristles on the beak.
Three other similar species of Eriogonum occur within or near the range of Crosby’s buckwheat in Oregon: E. prociduum, E. cusickii, and E. ochrocephalum var. calcareum. Eriogonum prociduum is distinguished from Crosby’s buckwheat by its glabrous scapes (versus usually floccose to tomentose and/or glandular scapes) and its involucres, glabrous or floccose only on the teeth (versus usually floccose or tomentose throughout, or glandular); E. cusickii has loose umbellate-cymose inflorescences, usually with only one involucre per node (versus tightly capitate clusters of several involucres); and E. ochrocephalum var. calcareum has, on average, longer scapes, (6-) 10-40 (-50) cm, that are usually glabrous or rarely slightly floccose (versus scapes 0.2-15 (-18) cm and usually floccose to tomentose and/or glandular) and involucres that are sparsely floccose or glabrous (versus usually floccose or tomentose throughout, or glandular).
When to survey
Surveys for Crosby’s buckwheat should be completed when the species is flowering, typically June through July.
In Oregon, Crosby’s buckwheat is restricted to light-colored (white and tan) tuffaceous sandstone substrates, usually on rounded, gentle slopes where the rock has not crumbled into fragments, at elevations ranging from 1600-1670 m (5250-5460 ft).
Although vegetation is sparse on the sedimentary tuff outcrops, there are a number of plant species that commonly occur with Crosby’s buckwheat, including Artemisia spp., Astragalus spp., Atriplex confertifolia, Ericameria spp., Erigeron linearis, Eriogonum spp., Stenotus acaulis, Ipomopsis congesta, Penstemon spp., Poa spp., Scutellaria nana, Stipa spp., and Tetradymia spp.
Crosby’s buckwheat was once thought to be restricted to southeastern Oregon (in Guano and Coleman Valleys in southeastern Lake County and Fish Fin Rim in southwestern Harney County) and northwestern Nevada. Although the distribution of the species in Oregon remains the same, Reveal’s (2005) treatment of Crosby’s buckwheat in the Flora of North America has broadened the concept of the species. As currently defined, Crosby’s buckwheat is widely scattered in valley bottoms, foothills, and mountaintops in central Idaho and western Montana, and is disjunct to southwestern Idaho, southeastern Oregon, northwestern Nevada, and also Elko County, Nevada.
A status review will be necessary to determine if this geographic re-interpretation of the species might lead to de-listing of Crosby’s buckwheat by the State of Oregon.
Species of Concern
Crosby’s buckwheat is threatened by range improvement projects and grazing by livestock and rabbits. Habitat loss due to gold mining activities poses a risk to the long-term survival of the species. Several Crosby’s buckwheat occurrences have been significantly harmed or destroyed by mining operations. Off-road vehicle use also poses a potential hazard for the species.
Did you know?
Bureau of Land Management botanist Virginia Crosby discovered Crosby’s buckwheat in 1978 in the southern end of Guano Valley in Lake County, Oregon while conducting a floristic survey of the Lakeview District. James Reveal described the species in 1981, naming it in Crosby’s honor.
Anonymous. 1979. Peggy Crosby finds new buckwheat species! Bulletin of the Native Plant Society of Oregon 12: 1.
Kaye, T., W. Messinger, S. Massey, S. Kephart, and D. Flanagan. 1990. Eriogonum crosbyae and E. prociduum inventory, reproduction, and taxonomic assessment. Unpublished report for the U.S. Bureau of Land Management, Lakeview District. Oregon Department of Agriculture, Salem, 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.
ORBIC (Oregon Biodiversity Information Center). 2010a. Rare, threatened and endangered species of Oregon. Institute for Natural Resources, Portland State University, Portland, Oregon.
ORBIC (Oregon Biodiversity Information Center). 2010b. ORBIC element occurrence database. Portland, Oregon.
Reveal, J. L. 1981. Notes on endangered buckwheats (Eriogonum: Polygonaceae) with three newly described from the western United States. Brittonia 33:441-448.