Rhododendron

Hello! A normally happy, fifty-year-old rhododendron, comfortable survivor of dry and deluged summers, is currently showing an unusually large number of yellow/dead leaves. It seems much more pronounced than any expected senescence. Soil is shale-y and quite well drained and there has been reasonable rainfall through the summer. I'm hoping it's not sudden oak death as there have been local cases, but the leaves are not marked or shrivelled. Does anyone have any other ideas what it might be?

 

With the increased rain amounts recently, as the water leaches away, it can make an acidic soil, more towards Alkaline. The whole of the leaves look yellow, and it appears that there is no disease, as you would expect marks on the leaf. Check the PH levels, of the soil, and adjust the level accordingly.

 

Hi,

Interesting, but not sure how Acidic rain into Acid soil can make it Alkaline ?
Assume its washing away certain properties, but no idea what ? or whats the best way to restore our fine clayish soil to an acidic state once these winter rains and bits of flooding have ended ?

 

Sulphate of Iron

 

Rhododendrons require a pH from 4.5-6.0 4.5 is generally considered a very low level for plants.

Such a margin provides quite a range. The general practice of changing/improving pH affected soil is. To increase acidity adding peat and or vegative compost to the soil. Sulphate of ammonia may sometimes be applied, in which case the nitrogen content of the soil may become affected. To raise the pH, lime can be added at any time.

I have always been somewhat mystified about the pH for Rhodos. Visiting the South of England and the IOW, Rhodos appear to flourish everywhere. Generally considered to be surface rooting, they do very well on the minimum depth of acidic soil that within a couple of inches lies on top of chalk.

Imho.I world be inclined to hang fire. Wait, give the wet weather a chance to stop, and then allow the soil to drain out. To apply sulphate of iron. Yes it will increase acidity but it is often used to get rid of moss and add nitrogen to lawns and the like. Hope this helps.

 

Thanks, all, for your replies. The rhody has revived very well on its own, it seems. The advice to hang fire appears to have been sound. Thanks once again, everyone.