bloody dock vs yarrow

bloody dock

noun
  • A herb named for its characteristic red or purple veins, used in moderate amounts in salads and as ornamental vegetable, Rumex sanguineus. 

yarrow

noun
  • Any of several pungent Eurasian and North American herbs, of the genus Achillea, used in traditional herbal medicine. 

  • The green woodpecker, Picus viridis. 

  • Common yarrow, Achillea millefolium, the type species of the genus. 

How often have the words bloody dock and yarrow occurred in a corpus of books? (source: Google Ngram Viewer )