Posted: 05/11/2017 at 20:15
I'd reckon planting a 15 yr old tree was always going to be a risk, unless you really know what you're doing.
Adding to that by planting it in a less than ideal location, and it's not surprising it hasn't really thrived. Without adequate watering until fully established, a mature shrub or tree will struggle. That's the main reason for the shrivelling and die back. The preparation of the hole it's planted in is also important in getting anything mature established.
You may be too late in trying to do anything about it now. Pruning it back to a healthy point at each stem might help, but if it's in a windy exposed site, it will always find it tough to look good.
Sorry if that's not very encouraging, but you may have to resort to moving it to a better (and well prepped ) spot, cutting it back and crossing your fingers.