I am doing some gardening for a family member who has a very sick Rhodadendrin. She has three beautiful 12 footers on the side of her house, and they are very healthy and happy. She has three others on the other side of her house and they are small, just planted last year and now they look like this, this and this . Has anyone seen this before in a rhody? Is the soil not acidic enough? Or too much perhaps? How about sun, they are in darn near full sun all day. I’d hate to transplant them, but if I have to I will. Any suggestions?
Yeah–run, don’t walk, to your nearest County Extension Office with the pix, unveil your tale of woe, and they will have the problem diagnosed in jigtime.
If you’ll give me a state and county, I’ll look 'em up for you online. Sometimes they even have a map for how to get to where they are.
Do you know what variety they are? Also, are they Encores?
My first guess is powdery mildew. You can use a fungicide to protect new growth, although I believe it won’t do much for leaves already affected.
The best key is prevention. Acidity and sun are two good places to start. Is the soil naturally acidic or did she bring some in? Does she fertilize at the proper times? An elevated, well-drained bed is key too. The fact they’re healthy on one side and hurting on the other makes me wonder if light exposure isn’t an issue too. You’re how far north, which plant zone?
Also, new planting seem (in my experience) to be much more susceptible to lace bugs. Those don’t look like they have them but have you checked the underside of the leaves?
Sunburn can cause the yellow leaves. The spots could just be a separate problem, like some sort of fungus. It’s not chlorosis, because the veins would still be green.
I’m in Connecticut on the coast. The rhodys are on the south side of the house, they get good sunlight nearly all day…perhaps too much. I don’t know what variety they are as they are so young…I have not seen a bloom yet so I’m not sure and I wasn’t there when they were bought.