American winterberry vs Michigan holly

American winterberry

noun
  • Ilex verticillata, a species of holly native to eastern North America in the United States and southeast Canada, from Newfoundland west to Ontario and Minnesota, and south to Alabama. 

Michigan holly

noun
  • American winterberry, Ilex verticillata. 

How often have the words American winterberry and Michigan holly occurred in a corpus of books? (source: Google Ngram Viewer )