hogweed vs richweed

hogweed

noun
  • Any coarse weedy herb. 

  • An umbelliferous plant, of genus Heracleum, most species of which are phototoxic. 

  • Certain plants from the genera Ambrosia, Erigeron, or Heracleum. 

richweed

noun
  • Pilea pumila, a herb of the nettle family with a smooth, juicy, pellucid stem. 

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