yellow leaves on Rhododenron

Question

Hi I have an old large Rhododendron that flowered well this year but flowers were smaller, so put down ecricaceous compost and sprayed with miracle grow
shrub feeder

Just in the last couple of weeks has developed yellow leaves all over the shrub, there are some green leaves with buds

downloaded photo

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Answer 1

It may be leaf senescence, or the falling off of leaves after a 2 to 3 year period. Here are more ideas:

https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/yellow-rhododendron-leaves.htm