I'm struggling to find a book that I read in the mid-1990's (published before 1995, probably, definitely before 1996). It would have been geared towards teens or pre-teens.
It is set in a small, impoverished town, in the middle of a drought and features someone (or something?) going around and granting wishes but (expectedly) the wishes all go wrong. One girl wishes that her beaux would "root up" and stay in town, but instead he starts turning into a tree. A boy wishes that that he would be able to find water with a dowsing rod but that only starts a flood.