Answer: It's natural for some of the older rhododendron leaves to turn yellow and fall off, to make way for new leaves. The older leaves are lower down on the stems. If newer leaves are turning yellow, it might indicate iron chlorosis (especially if the main leaf veins are still dark green), or it could indicate a root rot problem. You can fertilize the rhodies to combat chlorosis, but root rots are difficult to overcome. If the leaves wilt and roll downward yet remain attached to the plant, I'd suspect root rot from poorly draining soils. Affected plants should be removed and destroyed. Do not replant into the same hole. To avoid root rots, provide good soil drainage, maintain proper nutrition and soil pH, and purchase healthy plants from reputable outlets.
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