Why does your Rhododendron brachycarpum have sudden leaf drop? Diagnose the cause and fix it with our step-by-step guide.
As an acid-loving evergreen, R. brachycarpum is highly susceptible to waterlogged soil which promotes Phytophthora species. This pathogen destroys the fine feeder roots, leading to a sudden inability to transport water and subsequent leaf abscission.
Short-calyx Rhododendrons have relatively shallow root systems that cannot tolerate significant drying cycles. Sudden leaf drop is a common defense mechanism to reduce transpiration when moisture levels fall below the wilting point.
Extreme fluctuations, especially late spring frosts or sudden heatwaves, can damage the vascular tissue of R. brachycarpum. This physiological stress triggers a rapid shedding of leaves to protect the woody structure.
While usually a slower process, a sudden lack of available nitrogen in highly leached acidic soils can cause older leaves to yellow and drop rapidly. This is common if heavy rains have washed out the soil's cation exchange capacity.
Your plant might also be experiencing one of these issues:
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