harebell vs witloof

harebell

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

witloof

noun
  • Belgian endive, common chicory (Cichorium intybus) 

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