cornflower vs wild bachelor's-button

cornflower

adj
  • Of a blue colour, as that of the cornflower; cornflower blue. 

noun
  • Cornflower blue. 

  • A plant of the species Cichorium intybus. 

  • A small annual plant in the family Asteraceae, Centaurea cyanus, usually with bushy blue flowers which grows natively in European cornfields (i.e. wheatfields). 

wild bachelor's-button

How often have the words cornflower and wild bachelor's-button occurred in a corpus of books? (source: Google Ngram Viewer )