I have several Robellini's, 10 years old, inland So. Calif. They seem healthy, but two of them (3 trunks each), have one trunk that has fallen to the ground, but is still alive. The other two trunks are OK. I've put a stake in the ground, wrapped a rope around the fallen trunk, and pulled the wayward trunk back into place. All seems ok. Is there a better way to prop up the problem trunk? Can this trunk regain it's strength? Is there a known cause of weakness in one trunk of a multi trunk tree?