1 April 2008 New Rosa (Rosaceae) in California and Oregon
Barbara Ertter, Walter H. Lewis
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Two new roses are described from California and adjacent Oregon, with keys to distinguish each from the typical representative of their respective species. Rosa pisocarpa A. Gray subsp. ahartii Ertter & W. H. Lewis differs from typical R. pisocarpa by generally having fewer and larger leaflets, fewer flowers, and sepals that are most commonly eglandular, among other features. It is the characteristic member of the R. blanda Aiton complex in the northern Sierra Nevada and southern Cascade Range, where existing collections have been variously identified as R. pisocarpa, R. woodsii Lindl. subsp. ultramontana (S. Watson) Roy L. Taylor & MacBryde, R. californica Cham. & Schltdl., and R. bridgesii Crépin ex Rydb. The rank of subspecies is used to indicate a significant ecogeographic component of the species' range. In contrast, varietal rank is used for a localized expression of R. gymnocarpa Nutt. occurring on open ultramafic substrates in northwestern California and adjacent Oregon, described here as Rosa gymnocarpa var. serpentina Ertter & W. H. Lewis. Diagnostic characters include relatively short stature, fewer and blunter leaflets, and pedicels that are frequently eglandular.

Barbara Ertter and Walter H. Lewis "New Rosa (Rosaceae) in California and Oregon," Madroño 55(2), 170-177, (1 April 2008). https://doi.org/10.3120/0024-9637(2008)55[170:NRRICA]2.0.CO;2
Published: 1 April 2008
new taxa
Rosa gymnocarpa
Rosa pisocarpa
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