Before you cut up your plum tree, here is something you might try. Over a year ago, a tornado went though our orchard and took down all of the apple and plum trees. Some were snapped off, but some were just laid over. We took the tractor and pulled the undamaged trees upright. We then put cables on them and secured them to steel post we had set. We used sections of garden hose to protect the trees from the cable. A year and a half later all of the trees we set back up, re-rooted and are healthy and producing fruit. So don't give up on it if it is not snapped off.