Article (magazine)  (Jan 2022)  Page(s) 12.  Includes photo(s).
 
R. bridgesii, the currently accepted name for the Sierra ground rose, was discovered in 1857 by the English botanist Thomas L. Bridges. Its leaf surface is covered with a white tomentum but the hips are smooth.....R. calvaria ....Recognized as a synonym of R. bridgesii having the same botanical features....

Website/Catalog  (2018)  
 
Rosa bridgesii Crépin ex Rydberg, Bull. Torrey Bot. Club. 44: 83. 1917.(name conserved)
Sierran ground rose
Rosa gymnocarpa Nuttall var. pubescens S. Watson; R. spithamea var. solitaria L. F. Henderson; R. spithamea S. Watson var. subinermis Engelmann
Description...

In the phylogenetic analysis by A. Bruneau et al. (2007), Rosa bridgesii and R. spithamea comprise a distinct clade more closely related to Asian species than to others from western North America.
Rosa bridgesii has been conserved against R. calvaria Greene, R. covillei Greene, R. crenulata Greene, R. myriadenia Greene, and R. yainacensis Greene (B. Ertter 2007b). Only R. calvaria and R. crenulata are unambiguous synonyms of R. bridgesii; the taxonomic identity of the other names remains unresolved and may involve hybridization with other species.
On the basis of pollen size, E. W. Erlanson (1931) believed that material falling within the current circumscription of Rosa bridgesii was tetraploid (2n = 28). In a subsequent paper (1934), she reported a diploid somatic count (2n = 14) for R. calvaria, a synonym of R. bridgesii. Recent flow cytometry indicates a tetraploid condition for the sampled specimen of R. bridgesii (A. Bruneau et al., unpubl. data). It is possible that both ploidy levels are present within the species.

Article (newsletter)  (Aug 2014)  Page(s) 4.  
 
R. bridgesii exhibits few prickles and produces roses only in small clusters of two or more and stipules that are ciliate, i.e., with distinct hairs or glands. According to botanist Barbara Ertter, it appears to grow no hips.
Could Rosas spithamea, pinetorum, and bridgesii, all three ground roses and genetically tetraploid, be subspecies of R. gymnocarpa, a diploid? Possibly. According to rose species authority Cassandra Bernstein, “Widely distributed diploid plant species that spread into extreme environments”— and R. gymnocarpa can be found from the understory of redwoods to the understory of oaks, from the Sierra Nevada foothills to the Pacific coast —“have been known to mutate, evolve, or hybridize into different ploidies than those commonly reported.” Surely, then, the three ground rose species may be the same rose whose ecogeographic variations have created variations in the species.

Article (website)  (2007)  
 
Subgenus Rosa, Section Gymnocarpae
Rosa bridgesii Crépin ex Rydberg
Flowers commonly solitary; terminal leaflet very blunt and flat; leaf margins widely serrated; leaves finely hairy; prickles paired at nodes; open forest floors at elevations of 3000 to 6500 feet of the central and southern Sierra Nevada and southern Cascades.
Rosa bridgesii described here replaces the inland Rosa pinetorum described by Munz in A Flora of California (1959) and R. spithamea and R. gymnocarpa var. pubescens in the Sierra Nevada.
Gives detailed explanation of status of nomenclature and possible synonyms:
R. calvaria Greene; R. crenulata Greene; R. dudleyi Rydb.; R. gymnocarpa var. pubescens S. Watson; R. lesterae Eastwood; R. spithamea var. subinermis Engelm.; and R. yainacensis Greene.

Article (website)  (2007)  
 
R. yainacensis may or may not represent the same species as Rosa bridgesii. Recent field work in the presumed locality of R. yainacensis, Yainax Ridge in Klamath County, Oregon, has not produced specimens of R. yainacensis for study.

Article (magazine)  (2007)  
 
R. bridgesii typical ploidy 2x

Article (magazine)  (2007)  Page(s) 962-964.  
 
Ed. note: Barbara Ertter explains why the name Rosa bridgesii Crépin ex Rydberg should be "conserved" (a technical term meaning allowed as an exception to the rules of taxonomic nomenclature).

@ p. 964: As currently understood (Ertter in Fl. N. Amer. 9, in press), there is a relatively well-defined dwarf rose characteristic of mid-montane forests of the western Sierra Nevada and Cascade Range of California and southern Oregon that includes not only Bridges 62 but also with certainty the types of R. calvaria, R. crenulata, R. dudleyi, R. lesterae Eastw. (in Leafl. W. Bot. 3: 262. 1943), R. gymnocarpa var. pubescens, and R. spithamea var. inermis Engelm. (in Bot. Gaz. 6: 236. 1881), probably that of R. spithamea var. solitaria L.F. Hend. (in Rhodora 33: 204. 1931), and possibly those of R. covillei, R. myriadenia, R. oligocarpa Rydb. (l.c.: 532. 1918), and R. yainacensis.

Book  (Apr 1993)  Page(s) 514.  
 
R. yainacensis Greene, Species (Old Garden Rose), (R. myriadenia Green; R. yainacencis); Cultivated 1912. Allied to R. nutkana; Tetraploid...

Book  (1993)  
 
R. bridgesii
Dwarf shrub, dark brown stems, few prickles. Leaflets more or less hairy. Flowers, 2.5-4 mm (sic); open forests and rocky areas of Cascade Range and Sierra Nevada in Oregon and California. Synonym: R. gymnocarpa var. pubescens S. Watson

Book  (May 1992)  Page(s) 214.  
 
R. yainacensis, R. myriadenia N. America circa 1912. Closely resembling R. nutkana to which it is obviously related. Smallish but numerous deep lilac-pink flowers...