Christmas berry vs Duke of Argyll's tea tree

Christmas berry

noun
  • Synonym of spiceberry (“plant or its berry”) 

  • Synonym of toyon (“plant or its berry”) (Photinia arbutifolia, syn. Heteromeles arbutifolia) 

Duke of Argyll's tea tree

How often have the words Christmas berry and Duke of Argyll's tea tree occurred in a corpus of books? (source: Google Ngram Viewer )