( saying ) used to tell sb not to use sth or spend money carelessly because you do not have a lot of it
IT / MONEY DOESN'T GROW ON TREES
Meaning of IT / MONEY DOESN'T GROW ON TREES in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005