pigeonweed vs pokeberry

pigeonweed

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

pokeberry

noun
  • Synonym of pokeweed (the plant Phytolacca americana or its dark red or purple fruit). 

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