bigroot morning-glory vs manroot

bigroot morning-glory

manroot

noun

  • A flowering plant in the gourd family (Cucurbitaceae), genus Marah, native to western North America. 

  • Ipomoea leptophylla 

  • Ipomoea pandurata 

How often have the words bigroot morning-glory and manroot occurred in a corpus of books? (source: Google Ngram Viewer )