cornflower vs mare's-tail

cornflower

noun
  • A plant of the species Cichorium intybus. 

  • Cornflower blue. 

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

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

mare's-tail

noun
  • Equisetum, a fern ally 

  • especially, common mare's tail (Hippuris vulgaris) 

  • Erigeron canadensis (syn. Conyza canadensis), an annual weed 

  • A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud. 

  • Any aquatic plant of the genus Hippuris, having narrow leaves in whorls. 

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