'Mulberry trees' in the Bible

So David, asked again, of God, and God said to him, Thou shalt not go up after them, - get thee round, away from them, so shalt thou come in upon them, over against the mulberry-trees;

and it shall be, when thou hearest a sound of marching in the tops of the mulberry-trees, then, shalt thou go forth into the battle, - for God will have gone forth before thee, to smite the host of the Philistines.