milkweed vs wild cotton

milkweed

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

  • A monarch butterfly (Danaus spp). 

  • Euphorbia peplus and Euphorbia heterophylla, in order Malpighiales. 

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

wild cotton

noun
  • Cotton grass (Eriophorum spp) 

  • Any of several plants of the genera Abutilon and Hibiscus, especially Hibiscus moscheutos 

  • Any of the cultivated cottons that have escaped and established themselves in the wild. 

  • A tall weed, resembling milkweed, with a ball-shaped seed pod, Gomphocarpus fruticosus (syn. Asclepias fruticosa) and Gomphocarpus physocarpus (syn. Asclepias physocarpa). 

  • A shrubby herb (Gossypium thurberi) of southern Arizona and Mexico 

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