I would suggest major pruning for this tree in spring right before its main growth cycle starts in multi-season zones, but I'm not sure your state has that big a fluctuation so any time should be good. Just make sure you use a good cut paste to seal the wound and be aware this plant is prone to die-back so be sure the branches pruned are not cut completely flush with the trunk. leave a little bit on and after it dies off you can then remove the rest.