ground laurel vs trailing arbutus

ground laurel

noun
  • Epigaea repens, a low, spreading shrub found throughout eastern North America. 

  • Used other than figuratively or idiomatically: see ground, laurel. 

trailing arbutus

noun
  • The mayflower, Epigaea repens, of eastern North America. 

How often have the words ground laurel and trailing arbutus occurred in a corpus of books? (source: Google Ngram Viewer )