(2005)  Page(s) 453.  
 
R. x hollandica: In the British Isles and elsewhere, naturalized R. rugosa may be confused with a morphologically similar taxon of unclear origin and nomenclature. In continental Europe, it has most often been referred to the hybrid R. × kamtchatica Vent., which is said to have been introduced to France around 1770 (Bean 1980). However, recent authors hold that the introduced European plants are not identical to the native Far Eastern ones. Rutherford (1990) suggested that the name R. × hollandica should be used for this taxon, allegedly originating from a chance crossing in the Netherlands in 1888 between R. rugosa and an unknown species. Several species have been proposed as the other parental species. Most likely it is one of the diploid species R. majalis Herrm. or R. davurica Pall., which are closely related. The tetraploid R. palustris (Verrier 1991; in which case the name would be R. × spaethiana ‘Hollandica’) and the cultivar R. × noisettiana ‘Manettii’ (Mang 1985) have been suggested as well. The flower flavonoid pattern supports the ancestry of one of the diploid species R. multiflora Thunb., R. davurica or R. wichuraiana Crépin (Mikanagi et al. 1994). Possibly, hybrids between R. rugosa and more than one species have escaped from cultivation and are now recorded under the name R. × hollandica.

(2005)  Page(s) 452.  
 
In its native range [R. rugosa] hybridizes with R. davurica Pall. (syn. R. amblyotis C.A. Meyer) (Pimenov & Schroeter 1964 Ohwi 1965), with R. marretii Lév., which is its closest relative (Wu et al. 2000, 2001), with R. acicularis Lindl. (Charkewicz 1996), and with R. multiflora Thunb. (= R. × iwara Sieber ex Regel, syn. R. × yesoensis (Fr. & Sav.) Makino).

(2005)  Page(s) 452.  
 
The hybrid [of Rosa rugosa] with R. davurica, often called R. x kamchatica Vent., probably arose spontaneously in southern Kamchatka, where R. rugosa occurs on the coast and R. davurica in the central highlands....

(2005)  Page(s) 452.  
 
In North America, spontaneous hybrids [of Rosa rugosa] with the native rose speices R. carolina L. (=R. × koehneana Rehder) and R. palustris Marsh. (= R. × spaethiana Graebner) have been reported; however, only the former has been verified....

(2005)  Page(s) 453.  
 
Hybrids between R. rugosa and many species with irregular meiosis have been synthesized. Many of the hybrids have been named and grown for ornament (extensive overviews are given by Rehder 1949; Sokolov 1954; Bean 1980; Verrier 1991; Dickerson 1999; Spethmann & Feuerhahn 2003). Two synthetic hybrids have been found as escapes from cultivation, viz. a hybrid with R. majalis Herrm. (= R. × majorugosa Palmén & Hämet-Ahti) in Finland and European Russia (Palmén et al. 1995; Buzunova 2001), and one with R. nitida Willd. (= R. × rugotida Darthuis) in Sweden (Bertilsson et al. 2002). Rosa rugosa × multiflora has been reported as an escape in Germany (Mang 1985). The hybrids have probably escaped through dumping of garden refuse as they are generally unable to produce viable seeds.

(2005)  Page(s) 452.  
 
Formation of spontaneous hybrids [with Rosa rugosa] has been reported to occur with three polyploid species in the British Isles...
R. canina = R. x praegeri Wolley-Dod
R. mollis Sm. = R. x mangii Eigner x Wissemann
R. caesia Sm.

(2005)  Page(s) 452.  
 
Formation of spontaneous hybrids [with Rosa rugosa] has been reported to occur with three polyploid species in the British Isles...
R. canina = R. x praegeri Wolley-Dod
R. mollis Sm. = R. x mangii Eigner x Wissemann
R. caesia Sm.