pigeonweed vs white alder

pigeonweed

noun
  • Synonym of pokeweed (“the plant Phytolacca americana”) 

white alder

noun
  • American winterberry (Ilex verticillata). 

  • Grey alder (Alnus incana) 

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