Article (magazine)  (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....

Book  (1981)  Page(s) 271.  
 
R. x koehneana Rehd. (= R. carolina x R. rugosa). Shrub low, broad, very dense, stems with small infrastipular prickles, but otherwise internodes mostly without prickles; leaflets 7, oblong, simply serrate, bald above, hairy beneath; flowers solitary, purple, 6 cm./2.4 in. across, very floriferous; calyx-tube ovoid, bald, sepals long, with short bristles; pedicels 2.5 cm./1 in. long, thin, bald. 2n = 21, WR 203 (as R. humilis x R. rugosa). Originated before 1893 in the USA.