cow parsnip vs portulaca

cow parsnip

noun
  • Any umbelliferous plant of genus Heracleum. 

portulaca

noun
  • Any plant in the genus Portulaca 

  • Any of many tropical trailing herbs, of the genus Portulaca, having showy flowers 

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