Book  (2019)  Page(s) 129.  Includes photo(s).
 
Natural Hybrids...Rosa x iwara Siebold ex Regel, Index Sem. Hort. Petrop. 1861:53 (1861), description

Magazine  (2016)  Page(s) Table S2.  
 
rosa iwara and iwara1, Origin of the sample: Loubert Rose Garden, Genetic group 12, Percentage of assignation: 99.1, 1831, HMult, Regel, Origin: Asia, Ploidy: 2, measured

Newsletter  (Dec 2013)  Page(s) 33.  
 
[From "Seizo Suzuki’s collection of old roses and species roses", by Yuki Mikanagi]
In 1942, though Japan had already entered into World War II, Mr. Suzuki was continuing his field work, and found a natural hybrid between R. rugosa and R. multiflora (R. x iwara) near the estuary of the Toyohira River in Hokkaido, and a natural hybrid between R. rugosa and R. luciae (= R. wichurana) on the seashore in Ibaraki

Website/Catalog  (2006)  
 
Ko-Hamanasu (Small Shore Aubergine) syn. =Ko-Hamanashi (Small Shore Pear)
R. x iwara Siebold ex Regel
Index Sem. Hort. Petrop. 1861:53 (1861)
Estimated parentage: R. multiflora x R. rugosa

Article (magazine)  (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).

Book  (11 Jun 1993)  Page(s) 28.  
 
R. multiflora x R. rugosa. Japan before 1830. Description. Small white single flowers with separated petals giving the blossom a blackberry-like appearance... Its name means "rose thorn" in Japanese.

Book  (Apr 1993)  Page(s) 263.  
 
Miscellaneous Old Garden Rose, white, (R. x iwara Siebold ex Regel; R. yesoensis Makino); R. multiflora x R. rugosa; Cultivated prior to 1830. Description.

Book  (1965)  Page(s) 541.  
 
Rosa X iwara Sieb. R. yesoensis (Fr. & Sav.) Makino; R. iwara var. yesoensis Fr. & Sav. - Ko-hama-nasu. Natural hybrid of No. 5 [R. rugosa Thunb.] and No. 1 [R. multiflora Thunb.], differing from No. 5 in the less prominently rugose upper leaf-surfaces, and with smaller flowers 3-4 cm. across. Occurs rarely along seashores in Hokkaido and n. Honshu.

Book  (1936)  Page(s) 365.  
 
R. Iwara (hybrid rugosa) Siebold 1856; R. rugosa Th. X R. multifl. simpl.; white, 3 cm., medium size, double, cup form, clusters of 5-15, growth 7/10. climbing, 1.25m. Imported from Japan. Sangerhausen

Magazine  (Jul 1930)  Page(s) 91.  
 
Rugosa ibara. — Siebold, hybride de rugosa et de R. multiflore.