Apium graveolens dulce vs celery

Apium graveolens dulce

celery

noun
  • A European herb (Apium graveolens) of the carrot family. 

  • The stalks of this herb eaten as a vegetable. 

  • A yellow-green colour, like that of a celery. 

How often have the words Apium graveolens dulce and celery occurred in a corpus of books? (source: Google Ngram Viewer )