hogweed vs lamb's quarters

hogweed

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

  • Any coarse weedy herb. 

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

lamb's quarters

noun
  • Any of several similar plants of genera Chenopodium and Atriplex. 

  • Chenopodium album, of the goosefoot family, sometimes used as a potherb 

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