ipomoea vs white-fleshed sweet potato

ipomoea

noun
  • Any of various twining plants of the genus Ipomoea with showy monopetalous flowers, including the morning glory, the sweet potato, and the cypress vine. 

white-fleshed sweet potato

noun
  • Synonym of white sweet potato 

How often have the words ipomoea and white-fleshed sweet potato occurred in a corpus of books? (source: Google Ngram Viewer )