Posted: 03/02/2016 at 11:46
I don't think it's lichen either - it looks wrong and also it's so regular where it's appearing. I think that hedge is on it's way out.
I'd grasp the nettle, cut them down and dig them out, replace the exhausted soil with a mix of good topsoil and some well rotted farm yard manure and plant a new hedge. Perhaps something that'll be a bit happier with what's turning out to be a damp spot - hornbeam perhaps? That'd look lovely clipped regularly so that it retains its coppery leaves through the winter.
Every dead plant is a new opportunity