It is hard to find a joke without a dirty word or two in it. Here is one
with none:


 Two tall trees, a birch and a beech, are growing in the woods.

 A small tree begins to grow between them, and the beech says to the

 birch, "Is that a son of a beech or a son of a birch?" The birch says he

 cannot tell.

 Just then a woodpecker lands on the sapling. The birch says,

 "Woodpecker, you are a tree expert. Can you tell if that is a son of a
beech

 or a son of a birch?" The woodpecker takes a taste of the small tree. He

 replies, "It is neither a son of a beech nor a son of a birch. It is,
however,

 the best piece of ash I have ever put my pecker in."