bloodroot vs devil's nettle

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. 

devil's nettle

noun
  • Achillea millefolium or common yarrow, a flowering plant native to temperate regions of the Northern Hemisphere. 

  • Dendrocnide sinuata (synonym: Laportea crenulata), a species of nettle in the family Urticaceae found in Australia and South Asia. 

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