Catawbiense grandiflorum is a hardy heat-tolerant rhododendron. I am guessing there is another problem. I would guess that your soil may be sandy if you are in Central NJ. Also, you said that you are planting under large trees. These trees have roots which along with the sandy soil by be making it hard for your rhody to get enough moisture and nutrients. Also, you need a good acidic soil. One thing that you could try would be to make a raised bed with good acidic garden loam for your rhody. Another would be to go around the rhododendron, outside the drip line, with a shovel cutting down to cut any tree roots that may be running under your plant. I have rhododendron beds 20' outside the drip line of trees and still have roots running through the beds that I have to cut off every few years.

Rarefind Nursery is not too far from you. Here are a couple good hardy purples that Hank Schannen sells there:

'Anah Kruschke' hardy sun-tolerant
'Purple Passion' extremely hardy

Here is a link that might be useful: Rarefind Nursery in Jackson, NJ.

Thanks for taking the time to answer my question.
NJ is mostly clay soil. I prepared the soil by mixing sand, clay, pine needles and compost. I raised the bed. I am sure tress do not have runners because I worked around this area to plant other shrubs.
The plant might have been stressed when I planted last fall. I bought the plant in the middle of the summer, and it had already flowered obviously. It sat on the container for a couple of months until September. Also I made the mistake of not removing the spent flower, and I donÂt see buds formed. Even if the plant bounces back I donÂt think it will produce flowers this season.
For this reasons I prefer to buy a new one, and learn from this experience. Unfortunately I started reading information from the rhododendron society website during the winter. So I am learning now about how to properly care for them.

Thanks again,
Lawnkid