clematis vs maiden's honesty

clematis

noun
  • Any plant of the genus Clematis, vigorous climbing lianas found throughout the temperate zones. 

maiden's honesty

noun
  • A plant of the species Clematis vitalba, evergreen clematis, a vine, native to the chalk and limestone soils of Britain, often considered invasive and noxious elsewhere. 

How often have the words clematis and maiden's honesty occurred in a corpus of books? (source: Google Ngram Viewer )