cold frame vs hothouse

cold frame

noun
  • A transparent-roofed enclosure, built low to the ground, used to protect plants from cold weather. 

hothouse

noun
  • A heated greenhouse. 

  • An environment in which growth or development is encouraged naturally or artificially; a hotbed. 

  • A heated room for drying greenware. 

  • A hot state in global climate. 

verb
  • To provide (a child) with an enriched environment with the aim of stimulating academic development. 

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