cultivate vs lessen

cultivate

verb
  • To nurture; to foster; to tend. 

  • To turn or stir soil in preparation for planting. 

  • To grow plants, notably crops. 

lessen

verb
  • To make less; to diminish; to reduce. 

  • To become less. 

conj
  • unless. 

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