This rhododendron was about half its size when we bought our house in 2009. For a few years it was beautiful. Now it has black spots and the bark is crackled - it doesn't look at all healthy. This year we don't have as many blooms. Wondering if we should try to save it. New growth looks great! It gets full sun and water 2-3 times a week throughout the spring and summer. Seemed very happy until the last 2 or so years.
Rhododendrons can live for decades, so it should be worthwhile to solve the problems this one is having.
The leaf spots look fungal. After bloom is over, you can prune it back and spray the foliage with a copper fungicide. Be sure not to overfertilize, which can encourage growth more susceptible to problems.
An established rhododendron should not need watering except during an extended drought. When you do water, be sure water is applied at the base of the plant, not on the leaves. Leaves wet down too often encourage fungal problems.
You might want to do a soil test in that area. Rhodies like a low pH, and the soil near foundations tends to get more alkaline over time. You can get information on doing soil tests by clicking on the Soil Testing icon on the right side of our homepage.
Here is a good diagnostic pub for azaleas and rhododendrons: http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG51_IPM_A...