Too much heat and not enough water would probably be showing browning after wilting of rhododendron growth. Without a picture, I would guess insect. If you lived in the east, rhododendron midge would be a possibility, aphid and white fly can also cause distorted new growth. Have you checked undersides for any visible signs of insect?

Had the same problem this year. We had some unseasonably warm weather in Feb., and many plants were breaking dormancy as a result. Then, we had some March and April freezes that distorted a lot of the new growth on my Hydrangeas and other trees and shrubs. The leaves coming on now all look fine. So, could you have had a freeze problem? Cheers

After hitting "Preview", I realized this post is LONG! Before you guys read enough to judge my intelligence and stop, I would like to thank all those that offered advice on this issue. Even if I don't quite show it, please don't think I don't value the experience I see here. In researching 2-4D, I found that it had a halflife of 10 days. I picked up the manure on Jan 31. Some of it was aged, some, not so much. Although the age is irrelevant as the manure may have become exposed to the herbicide after being... well, abandoned by the horse. Either way, whatever the concentration, it should have been at half strength on Feb 10, quarter strength on Feb 20, 1/8 strength on Mar 2, and 1/16 on Mar 12. Plants were planted on March 6. In looking at the docs provided by Jean, my plants appear to be much worse than the worst case scenario provided by the studies they did. However, with that said, it may not be 2-4D either, but something else that is more persistent. Or, there is the possibility that my neighbor sprayed something that I'm not aware of, possibly in his front yard (these are on the end of the bed closest to the front of the house...). Still, I would think that if this were drift, it would have affected more than just these four plants and the difference between plants four and 5 wouldn't be so evident. Either way, if it was the manure, and I believe we all agree that it is, I may still be OK. I don't care about these plants. There is nothing I can do about them anyway. Even if I were to pull them, I would have to put something else in their place and unless I dig out that whole end of the yard, I'd be putting new plants in the same position as the ones I'd be pulling. Besides, I'm in Texas. It's too late to be setting out. I've never put anything out this late and had it produce anything. The plants are going to have to die, grow out of it, or sit there and pout in a permanent prepubescent state. I had plants that had this issue last year on the other end of the same bed. They grew out of it just fine and ended up producing as well as anything else in my garden (it was not a good year). In the mean time, I'll keep soaking these plants to see if I can dilute down whatever is in the soil to levels were they are not longer an issue. If the plants die, the plants die. I have about 21 more. Like I said, these are experimentals anyway. Finally, I agree that this looks exactly like herbicide damage, and if you guys have not heard of anything other than herbicide that could cause this problem from horse manure, then we'll agree that this is herbicide damage. The main thing I was worried about was my compost pile. I used half the manure I retrieved that day on the spots these plants are now mixed the other half into my compost pile. The compost is about a year's worth and is finally finished. I used all I could this year and thought some manure and leaves now and coffee grounds through the year might keep it young and vibrant to be used for next year. While I'm sure it will be safe when next year's plants hit it in Feb-March of next year, I'll be sure to add some more materials to dilute any herbicide residuals that may persist. I was very worried that I was going to lose my compost pile (how sad is that?) The plants took 3 months to grow. I work on my compost piles year round!

Jennifer —-(Spraying with Neem Oil and or and other mixtures to eradicate the insects organically could still harm those beneficial insects. Some people will just let those pest stay on the tree because they dont want to harm them. Its a difficlt choice to make for some and you need to understand that some bad infestations that might get out of hand and could cause your trees to become weak and allow other diseses to slowly kill your tree. i always try and let Mother Nature work on the right balance of the pest verses the beneficial insets to keep everything in check. But sometimes i will have to step in and use more than organic to combact the problem. its up to you to decide what is best for your tree. Laura Even those that eat leaves ___ Katydids 🌺