Don't prune it, that will cut off any buds that may be there. Pruning doesn't help them bloom and isn't usually necessary.

Lack of sunlight can be a problem.

Thank you buyorsell888. I'll keep my pruners off the big guy then :) He was certainly getting a lack of sunlight where he was, maybe this move will help.

Cutting a plant back forces it to use stored energy to replace the lost top growth. A specimen in weak condition may not be able to muster a strong recovery, even die.

Severely reduced top growth indicates a pretty strong problem. Common banes of rhododendrons here are mildewing of the leaves, infestation of the roots and crown by honey fungus, and infestation of the roots and branches by water molds. Sudden oak death is also starting to be seen, perhaps this may become a major factor later. Don't know about rhododendrons specifically but on some plants the water mold causing this syndrome actually attacks the leaves as well as other parts of the shrub.

If it has honey fungus or water molds on the roots you don't want to be shuffling it around the place as the pathogen may then infest the new planting location(s).

Severely reduced rate of top growth indicates...

Thank you bboy. I will keep a close eye on the plant this spring. It doesn't appear to be showing any signs of disease or infestation but the "reduced top growth" issue is one to watch. The plant is at the very far end of the garden and not near a lot of things it can do damage too if it is ill.

Good news though is that there are new sprouts from the bottom and the top branches are showing budding. Today I think I may actually be seeing some flower buds being set!

Flower buds on rhodies are set over the summer, for the next spring's bloom. It could take a couple of years for your rhodie to respond to improved conditions. They are not full shade plants at all, so you did the right thing by moving it to more sun. Now just be patient.

Rhodies do NOT get sudden oak death. The same pathogen causes leaf and twig blight on rhodies but they do not get sudden oak death, which is a bark canker disease of tanoaks and some (not all) true oaks. In WA and OR it is a pathogen of nursery plants so your mature rhodie that's been in the garden for over a decade is not going to have it unless you buy a new plant and plant it right next to the older one. In CA forests where the trees are infested it can blow around some distance in the rain but not here, it is carried on nursery plants. We don't have the right kind of trees to get the same kind of spread they get down there.

Sure, you'll see many of our garden plants and native plants on lists of plants susceptible to sudden oak death, but all that means is that someone somewhere once found the pathogen on one of these plants or was able to induce the disease in a greenhouse inoculation trial. No PNW native plants have been found infected in the PNW, and the very few infected garden plants up here have all been recent purchases from nurseries supplied from either OR or CA. Someday it will spread beyond that, but not for some years probably.

There are a lot of different water molds (phytophthoras) that cause leaf and twig blights on rhodies. P. ramorum, the one that causes sudden oak death, is just one more. It does not cause root rot like most phytophthoras do.

"Phytophthora ramorum is a fungus-like organism well-adapted to the cool, wet conditions of the PNW and tolerant of heat and drought. Several spore types are produced that help this organism survive and spread. Spores may survive in potting media for 6 to 12 months. Spores landing on wet leaves or stems germinate and infect the plant. Young leaves are especially susceptible. Within a few days, sporangia are produced which release tiny swimming spores (zoospores). The sporangia themselves can also detach, germinate, and infect. Sporangia and zoospores can be moved with wind-borne rain, irrigation water, or with water splashed onto foliage. There are two mating types, designated A1 and A2. The forest isolates from California and Oregon are the A2 mating type, while the European isolates are mainly the A1 mating type. Both mating types have been isolated from Oregon nurseries but the A1 mating type has not been isolated in Oregon since 2003"

Here is a link that might be useful: Rhododendron -- Ramorum Leaf Blight and Shoot Dieback

Thank you both for some very informative posts. I found them very helpful. My rhody does not appear to have any of the symptoms of disease but rather signs of blackberry abuse. I am willing to give this plant some time to come around. I'm a soft hearted gardener. sigh. Even if it doesn't bloom that would be fine for where it is now.

It was helpful to hear that it might take a season or so to see anything if at all. It gives me a ball park idea for the plant's future. For now the birds are loving it and that's good enough for me.

Thank you!