Rhododendrons have irredescents on them - Ask Extension
What do I apply for this?
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Rhododendrons have irredescents on them #927313
Asked April 01, 2026, 7:40 PM EDT
What do I apply for this?
Washington County Oregon
Expert Response
Thank you for your question, Doug. There are no known diseases in our database with symptoms such as these, and I see no evidence of any insect infestations. These colorations may be evidence of a nutrient deficiency, potentially phosphorus. You can have your soil tested for nutrient deficiencies, generally, through the OSU Soil Clinic (https://cropandsoil.oregonstate.edu/shl/testing-services/soil-testing), or you can send samples of the plants' leaves to the OSU Plant Clinic (https://bpp.oregonstate.edu/plant-clinic/submit-sample/how-submit-plant-samples). If you use the latter, be sure to tell them whether this phenomenon is present on all of the plants' leaves, just the old leaves, or just the new leaves. Good luck!
