harebell vs horseweed

harebell

noun
  • A perennial flowering plant, Campanula rotundifolia, native to the Northern Hemisphere, with blue, bell-like flowers. 

horseweed

noun
  • Any of various flowering plants of the genus Conyza. 

  • A plant of the species Cichorium intybus 

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