My husband accidently backed into our monkey puzzle tree with his truck while turning around near it and broke off a section of one branch--not completely sheared off--we tried to tape it up in hopes that, miraculously, it may mend itself--what are the chances of that and if hopeless, what should I do to try to save the branch and the trees' beautifully symetric shape? It is approx. 8 ft. tall and has been planted for 3 years.
Depending upon how well you set the branch and how quickly you did it, it just might recover. Sort of like setting a bone and using a splint to keep it from moving. It might take just like a graft. If it does not, your tree will have a little "character", I guess. Perhaps with some luck it may shoot out some branches and fill in the "hole".
It is unlikely that the break can be mended - there'll be too much weight acting on the branch for the splinting to hold. However, Monkey-puzzles usually shed their low branches naturally anyway as they grow taller, so in a few years you'll not be able to see the damage any more.