Book  (2007)  
 
'Bertha' Shrub, light pink, 1948 Percy H. Wright. (R. rugosa x hybrid perpetual) x (R. multiflora x R. blanda) Includes description.

Book  (1967)  Page(s) 46.  
 
Some All-Canadian Roses
by Fred Blakeney, Victoria, B.C.
Mr. Percy Wright of Saskatoon, Sask., must be considered one of the foremost hybridizers of species and near species roses in North America. He has been working on these roses for many years, and knows the reactions of various hardy roses when crossed with species roses.
His objective has always been to produce worthwhile garden roses that are hardy enough to withstand the extremely low temperatures of the Prairies in winter. [...]
Here is a list of Mr. Wright's originations in chronological order of introduction:
1946 "Bertha", single, delicate pink on erect stems, somewhat like a hollyhock.

Website/Catalog  (1949)  Page(s) 13.  
 
"BERTHA* - another rose of the same ancestry [Royal Robe]. Very large single flowers, delicate pink, up and down an erect stem like hollyhocks, and full of charm."