starthistle vs thistle

starthistle

noun
  • Any of the genus Centaurea of herbaceous thistle-like flowering plants. 

thistle

noun
  • Any of several perennial composite plants, especially of genera Cirsium, Carduus, Cynara, or Onopordum, having prickly leaves and showy flower heads with prickly bracts. 

  • This plant used as a charge. 

  • The Order of the Thistle, or membership thereof. 

  • This plant seen as the national emblem of Scotland. 

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