knotgrass vs portulaca

knotgrass

noun
  • An annual plant, Polygonum aviculare, found in fields and wasteland 

  • Paspalum distichum, a weedy perennial grass of wet areas 

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 knotgrass and portulaca occurred in a corpus of books? (source: Google Ngram Viewer )