Hmm. I really don't know. I think they are black walnut trees since that is what commonly grows here in western NC. They are volunteers. I think the gardeners are squirrels!
Oregon grape is NOT a grapevine but rather a type of holly. It gets yellow flowers followed by dark blue berries. https://www.google.com/search?q=oregon+grape&source=lnms&tbm=isch&sa=X&ei=vSJtU5_gIpHJsQS4xoHYBg&ved=0CAgQ_AUoAQ&biw=1163&bih=638