Surveys for Astragalus asotinensis (Asotin milkvetch) near Billy Creek and Camp Creek, lower Snake River Canyon, Idaho

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Astragalus asotinensis (Asotin milkvetch) is a newly described plant species known only from a small area within the lower Snake River Canyon near the Idaho/Washington border south of Asotin, Washington. It was originally found on limestone substrates of the Martin Bridge Formation on Lime Hill in Washington and Lime Point in Idaho. More recently it has been found north of Lime Point, north and south of Billy Creek, and near Camp Creek on substrates mapped as Hurwal or Martin Bridge Formations. Both formations contain calcareous components and are composed of island-arc metasedimentary rocks. We conducted surveys in 2010 and 2011on Bureau of Land Management parcels that had portions mapped as Hurwal or Martin Bridge Formations. We found Astragalus asotinensis growing on calcareous substrates but not on non-calcareous substrates. During the course of this study, we also conducted incidental visits to occurrences of the following rare plant species: Cirsium brevifolium (Palouse thistle), Pyrrocoma scaberula (= P. liatriformis, Palouse goldenweed), and Silene spaldingii (Spalding’s catchfly).

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Reference Code: U12PEK02IDUS <br>

Full Citation: Pekas, K.M., K.L. Gray, and J. Lichthardt. 2012. Surveys for Astragalus asotinensis (Asotin milkvetch) near Billy Creek and Camp Creek, lower Snake River Canyon, Idaho. Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise. 16 pp. plus appendices. <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: {Astragalus asotinensis} <br>

Keywords: Astragalus asotinensis, Asotin milkvetch, lower Snake River Canyon, Canyon grassland, Hurwal Formation, Martin Bridge Formation, rare plant conservation, Idaho native plants, Cirsium brevifolium, Palouse thistle, Pyrrocoma scaberula, Pyrrocoma liatriformis, Palouse goldenweed, Silene spaldingii, Spalding’s catchfly <br>