herbal tea vs tea tree

herbal tea

noun
  • A beverage made by infusing the leaves of various herbs, generally not including true tea (Camellia sinensis). 

tea tree

noun
  • The tea plant (Camellia sinensis), from which black, green, oolong and white tea are all obtained. 

  • The tree Melaleuca alternifolia, from which tea tree oil is obtained. 

  • The shrub ti (Cordyline fruticosa). 

  • The kanuka, Kunzea ericoides. 

  • A shrub or small tree native to New Zealand and southeast Australia (Leptospermum scoparium). 

  • The duke of Argyll's tea tree (Lycium barbarum), also known as wolfberry or matrimony vine. 

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