pigeonweed vs red nightshade

pigeonweed

noun

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

red nightshade

noun

  • Phytolacca americana syn. Phytolacca decandra 

  • Solanum villosum 

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