Red Alder yellow leaves - Ask Extension
I have several red alder in my suburban backyard. All have been very healthy and gushing forth bright green leaves all spring. Suddenly in the last fe...
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Red Alder yellow leaves #874074
Asked June 21, 2024, 12:53 PM EDT
I have several red alder in my suburban backyard. All have been very healthy and gushing forth bright green leaves all spring. Suddenly in the last few weeks they have all begun to show yellow leaves that are now dropping from the tree. Interestingly, all the other leaves on the trees, at least so far, continue to look very healthy and green. We have had a very mild spring in west Portland, with intermittent sun and grey and rain. Seemingly not stressful conditions for the garden. Please let me know your thoughts. So grateful for this service, you've proven so helpful to me and my native garden over the years.
Washington County Oregon
Expert Response
Thank you for your question, Chuck. There are 11 diseases which impact alder species, and the one that causes yellowing is this: https://pnwhandbooks.org/plantdisease/host-disease/alder-alnus-spp-leaf-spot
But, without a lab examination of the leaf under a microscope, we are unable to make an accurate diagnosis. It may also be just the tree's reaction to a changing environment, or a nutrient deficiency or overwatering. I suggest that you send samples to the OSU Plant Clinic: https://bpp.oregonstate.edu/how-submit-plant-materials
Good luck!
But, without a lab examination of the leaf under a microscope, we are unable to make an accurate diagnosis. It may also be just the tree's reaction to a changing environment, or a nutrient deficiency or overwatering. I suggest that you send samples to the OSU Plant Clinic: https://bpp.oregonstate.edu/how-submit-plant-materials
Good luck!
