We've got PJM rhododendrons at our new house in Michigan... a couple of them are absolutely flourishing, but two of the smaller bushes right next to them are not having a good time. Some of the branches flowered sparsely this year, but about half the bush is woody and bare. I see buds, but they didn't open, and no new leaves are growing on these branches now. Two questions:
(1) Why? What caused this, and how can I prevent it in the future? Cold winter? Soil conditions? I got some Holly-tone but haven't applied it yet...
(2) How to fix it? I understand that you can prune as long as you do so above a growing center, and the buds have not set for next year. But some of these branches don't have a hint of green anywhere, all the way down to the ground. Should I lop them off and hope the rest of the bush fills out over the next few years?