Son of a b....?

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 she cannot tell.

 They argue all afternoon whether it is a son of a birch or a son of a beech. Just then a woodpecker lands on the sapling.

The birch says:"Hey Woody, you're a tree expert. Can you end this argument and tell us 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 into."