bloodroot vs milfoil

bloodroot

noun
  • A North American plant, Sanguinaria canadensis, of the poppy family, which has a red root and sap and a single white flower in early spring. 

milfoil

noun
  • Common yarrow, Achillea millefolium. 

  • Any of several similar pungent Eurasian herbs, of the genus Achillea 

  • Any plants of the genus Myriophyllum; water milfoil. 

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