autumn crocus vs pencil tree

autumn crocus

noun
  • Any of several species of genus Colchicum that bloom in the Fall 

  • especially, Colchicum autumnale. 

pencil tree

noun
  • Euphorbia tirucalli, a tree found in semi-arid tropical climates 

How often have the words autumn crocus and pencil tree occurred in a corpus of books? (source: Google Ngram Viewer )