Used as a variation of the common "
If there is grass on the playing field" used to determine if a girl is maature enough for sex; The "
grass" being her pubic hair. if there is no grass on the playing field, one must "go around back and play
in the dirt", as in engage in anal sex with the girl in question.
"Do you think shes
old enough?"
"
Doesn't matter, if there's no grass on the playing field, go around back and play
in the dirt."