bindweed vs morning glory

bindweed

noun
  • true bindweed (Convolvulus). 

  • slender bindweed (Polymeria calycina). 

  • bittersweet nightshade, blue bindweed (Solanum dulcamara). 

  • false bindweed (Calystegia). 

  • black bindweed (Fallopia convolvulus). 

morning glory

noun
  • Several members of the family Convolvulaceae; climbing plants with trumpet shaped flowers. 

  • An involuntary erection present upon waking. 

  • A rolling cloud in the shape of a cylinder. 

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