Japanese plum vs plum blossom

Japanese plum

noun

  • A fruit tree, Prunus mume. 

  • A fruit tree, Prunus salicina. 

plum blossom

noun

  • The blossom of the tree. 

  • A tree, Prunus mume, native to East Asia bearing an apricot-like fruit; the Japanese apricot or Chinese plum. 

  • Used other than figuratively or idiomatically: see plum, blossom. 

How often have the words Japanese plum and plum blossom occurred in a corpus of books? (source: Google Ngram Viewer )