Why does your Rhododendron arboreum have yellow leaves? Diagnose the cause and fix it with our step-by-step guide.
Rhododendrons are acid-loving plants; if the soil pH rises above 5.5, iron becomes chemically locked in the soil, preventing uptake. This typically manifests as bright yellow leaves with distinct dark green veins.
Excessive soil moisture or poor drainage in the heavy soils often used for R. arboreum leads to fungal pathogens attacking the root system. This prevents water transport, causing uniform yellowing and eventual leaf drop.
A lack of available nitrogen in the substrate causes the plant to mobilize nutrients from older leaves to newer ones. This results in an even, pale yellowing starting with the oldest leaves at the base of the tree.
While R. arboreum is a tree, it lacks deep-reaching taproots in its early stages and relies on consistent moisture. Prolonged dry periods cause leaves to lose chlorophyll and turn yellow before dropping.
Your plant might also be experiencing one of these issues:
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