lesser celandine vs pilewort

lesser celandine

noun
  • A European perennial herb, Ficaria verna, having heart-shaped leaves and solitary yellow flowers 

pilewort

noun
  • Ficaria verna (formerly Ranunculus ficaria), lesser celandine, a plant in the buttercup family. 

  • Erechtites hieraciifolius, or fireweed, a plant in the aster family; 

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