Yellow leaf drop

Question

Hi, my rhododendrons, but mainly the 8 year old one is dropping leaves that are yellow, some of the branches are yellow too. I fed it in early spring and given a tonic at least 3 times during the summer, the last time being about 2 months ago, but it has been like this the whole summer and now as the weather is cooling overnight, it appears worse.
Also, all the others are experiencing the same including my azalea.
I believe when they require water they also have yellowing leaves, so I have been watering as required.
Also, there does appear to a mild weevil attack going on , but I used a weevil killer for this, although I am not sure if they have been eradicated.
Is there anything else I can do before winter.?
Thank you in advance.

Answer 1

It sounds like your plants have a case of chlorosis, or iron deficiency. Amending the soil with sulfur and providing an iron fertilizer will help correct the problem. This applies to your azalea, as well.

Here are articles that will help:

https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/issues-with-rhododendrons.htm
https://www.gardeningknowhow.com/ornamental/shrubs/azalea/common-azalea-problems.htm
https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/yellow-rhododendron-leaves.htm