shrubbery vs undergrowth

shrubbery

noun
  • Shrubs collectively. 

  • A planting of shrubs; a wide border to a garden where shrubs are thickly planted; or a similar larger area with a path winding through it. 

undergrowth

noun
  • The plants in a forest which only reach a relatively low height (such as shrubs and bushes). 

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