crown flower vs milkweed

crown flower

noun
  • A large shrub, Calotropis gigantea, growing up to 4 meters tall, with clusters of waxy flowers that are either white or lavender in color. 

milkweed

noun
  • Also of the genus Calotropis in order Gentianales, family Apocynaceae 

  • Principally of the genus Asclepias in order Gentianales, family Apocynaceae 

  • A monarch butterfly (Danaus spp). 

  • Euphorbia peplus and Euphorbia heterophylla, in order Malpighiales. 

How often have the words crown flower and milkweed occurred in a corpus of books? (source: Google Ngram Viewer )