'Mulberry trees' in the Bible

Therefore David inquired again of God: and God said to him, Go not up after them; turn away from them, and come upon them over against the mulberry trees.

And it shall be, when thou shalt hear a sound of going in the tops of the mulberry trees, then thou shalt go out to battle: for God hath gone forth before thee to smite the host of the Philistines.