Surprised by tree

Went for a walk in the Pentlands this morning, intending to go up from Castlelaw on the SE slopes.

However, the military had got there first and the red flags were up round the firing ranges so we had to change route.

Walking up from Boghall we found ourselves above Woodhouselee and in what must once have been some finely planted policies. What we took for rough, boggy hill grazing turned out to have some substantial, carefully grouped rhodedendrons and a number of specimen trees, including this glaucous beauty (can someone identify it for me).

PS I am on holiday, not skiving!