pokeweed vs red nightshade

pokeweed

noun
  • A poisonous North American plant, Phytolacca americana, with reddish stems, broad leaves, clusters of white flowers, and dark purple berries. 

red nightshade

noun
  • Phytolacca americana syn. Phytolacca decandra 

  • Solanum villosum 

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