Clematis vitalba vs old man's beard

Clematis vitalba

old man's beard

noun
  • Used other than figuratively or idiomatically: see old, man, -'s, beard. 

  • Tillandsia usneoides, a bromeliad; Spanish moss. 

  • Clematis aristata, an Australian climbing plant. 

  • Clematis vitalba, a climbing plant. 

  • Chionanthus virginicus, a tree. 

  • Usnea, a type of lichen. 

How often have the words Clematis vitalba and old man's beard occurred in a corpus of books? (source: Google Ngram Viewer )