It would be equally easy for Nana to dump the leaves in her own trash bin/recycle bag/compost pile, but to her that's not the point.  It's not even in her equation that Rose treats Nana better than she has any right to expect, considering her behavior.  Why, then, does Nana dump leaves into Rose's yard?  She's just plain ornery, of course.  Today's Cartoon:  #1,157.  Suggestion Box:  pjones41@kc.rr.com.