apple pear vs pear tree

apple pear

noun
  • Pyrus pyrifolia, the tree that bears this fruit. 

  • A fruit of a northeast-Asian species of pear with a crisp, juicy texture and an apple-like shape. 

pear tree

noun
  • A tree of the genus Pyrus, which bears the pears as fruits. 

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