Article (magazine)  (Jan 2022)  Page(s) 10.  
 
....a rose growing at the Petrified Forest only two miles away as the crow flies, named Rosa sonomensis in 1891 by Edward L. Greene. (Today R. sonomensis is ranked as a synonym of R. spithamea.) On a survey of the Petrified Forest after the Tubbs Fire several years ago, I was walking its burned trails with owner Janet Angell when we came upon a large patch of R. sonomensis full of flowers. Janet was surprised to see them. She’d walked those trails many years and not seen rose flowers before. I explained that this rose is called a “firefollower.” With the overhead shading trees and shrubs reduced to ashes, the increase in potash and full sunlight initiates a flowering not seen under normally shady conditions. The low growing plants thrive, bloom and set lots of hips for years until overshadowed by surrounding shrub and tree growth. Gradually, they disappear beneath the soil, living as roots sending up only scattered sprouts with occasional flowers and rarely fruiting, patiently awaiting the next liberating fire.

Book  (1974)  Page(s) 39.  
 
Sonoma Ground Rose (Rosa spithamea sonomensis) This low growing rose is found in drier places, even in shaparral, from Sonoma County southward to San Luis Obispo County. Both the sepals and the unripe hips have glandular spreading hairs.

Book  (1970)  Page(s) 21-22, 160.  
 
The Effect of Fire: The summer-dried hills and mountains of California are unusually susceptible to devastating visitations of this element [fire] and in the form of brush and forest fires it has peridocially swept over the valleys and lower slopes for ages. The element of fire has, therefore, become a factor, at least of secondary importance, in the evolutionary development of the plant associations where it has been most prevalent, and in such associations, only the plants that are able to recover or reproduce between recurring fires have survived....This is especially true of the chaparral, for the shrubs that are found in it appear promptly after a burn either as vigorous crown sprouts or root sprouts or as fast-growing seedlings. Many...develop fast enough to flower and fruit during the first or second season of growth following a fire...After the extensive Marin County burn of 1945, the following trees and shrubs were observed to sprout from crowns or underground stems:...Rosa spithamea var. sonomensis
R. spithamea Wats. var. sonomensis (Greene) Jeps. Not uncommon on high rocky ridges and slopes in the chaparral; Mount Tamalpais (Matt Davis Trail, Rocky Ridge Fire Trail, Lake Lagunitas); Carson country; San Rafael Hills. -R. sonomensis Greene. When, between fires, the chaparral shrubs grow tall and thick, the Sonoma rose is not conspicuous and rarely blooms; but in the ashes of a burn the little rose is attractively floriferous and its fragrance is something to be remembered.

Book  (1944)  Page(s) 463.  Includes photo(s).
 
Rosa sonomensis Greene. Sonoma Rose. Fig. 2517.
Rosa sonomensis Greene, Fl. Fran. 72. 1897.
Rosa spithamaea var. sonomensis Jepson, Fl. W. Mid. Calif. 279. 1901.
Rosa granulata Greene, Leaflets Bot. Obs. 2: 262. 1912.

Plants much resembling Rosa spithamaea in size and general habit, differing chiefly in the leaflets which are broadly oval to orbicular, 5-15 mm. long, doubly serrate with glandular teeth, glabrous on both surfaces, firm and somewhat glaucous.
Local on high mountain ridges, Upper Sonoran and Arid Transition Zones; Sonoma and Marin Counties to San Luis Obispo County, California. Type locality: Petrified Forest, Sonoma County. May- Aug.

Book  (1939)  Page(s) 182.  
 
Rosa spithamea...Var. sonomensis (Greene) Jepson. Sonoma Rose.
Stems armed with numerous slender or stout straight or recurved prickles. Leaflets firm, ½-inch or less long, glaucous beneath. Flowers usually several in a cluster.
Sonoma Rose inhabits dry slopes of the outer Coast Ranges from San Luis Obispo County northward to Mendocino County where it is replaced by the species.

Magazine  (1917)  Page(s) 81.  
 
Rosa sonomensis Greene This is related to R. spithamaea, but differs from the other Californian species with prickly fruit in the firm glaucous leaves, the densely prickly stem, and the short sepals. California: Petrified Forest, Sonoma County, 1883, Greene; Mount Tamalpais, V. Bailey..., 1885...; Converse Basin, Fresno County, 1904. Dudley.

Book  (1911)  Page(s) 206.  
 
R. spithamaea Wats. var. sonomensis Jepson. Sonoma Rose. Branches several from the base, erect, mostly simple, 9 to 12 in. high, densely armed with stout straight or slightly recurved prickles.; leaflets 5, broadly ovate, 4 to 8 lines long, serrate, with teeth minutely glandular-denticulate; flowers small, several in a corymb; hips globose, 3 to 5 lines broad; calyx-lobes ovate-lanceolate, glandular hispid, rather closely erect in fruit. Rare montane species, on high dry slopes: Sonoma Co., Greene; Mt. Tamalpais, Jepson; Saratoga, Santa Clara Co., Davy.

Book  (1909)  Page(s) 211, Vol. 2.  
 
R. spithamea
Var. sonomensis Jepson Sonoma Rose
Stems densely armed with stout straight or slightly recurved prickles; flowers several in a corymb; calyx tube very densely glandular...dry slopes 50 to 2000 feet; outer Coast Ranges from San Luis Obispo County to Mendocino County

Book  (1891)  Page(s) 72.  
 
R. Sonomensis. Slender, 1 ft. high, with many flexuous very lafy branches well armed with straight prickles: stipules shorts, almost truncate, narrow, the margin closely glandular-ciliolate...leaflets 5,...broadly ovate...1/4-1/2 in. long, margin...coarsely serrate....fl. many, small, in dense terminal corymbs: calyx-tube round-pyriform, glandular-hispid; lobes....without foliaceous tips or appendages, erect in fruit.-At the Petrified Forest in Sonoma Col., collected by the author late in August, 1988, and distrubuted as R. spithamaea, to which it is allied, but from which the characters of leaflet and stipule abundantly distinguish it.