Rhododenron flowers rotting without opening

sarahgrahame

I've started a new thread as updating my thread from last year isn't getting responses.

Last year my Rhododendron nearly died during the heatwave. It seems to have recovered to a degree, and most of the leaves now seem to be healthy. Lots of flowers started to form, but instead of opening up, they stayed shut, turned yellow and went sticky before rotting completely. Only half a dozen of the very last ones have opened. I've googled but can't find any mention of this problem. 
On the old thread:
https://forum.gardenersworld.com/discussion/1019732/urgent-can-i-save-this-rhododendron/p1
...people suggested it might eventually need cutting right back. Should I try that? Below the newer growth the branches are bare, so it has top only foliage at this point.

Fairygirl

Hi Sarah - I think the problem has been caused by the dry weather last summer.
The new buds start forming in late summer, so if the  shrub itself was dry and struggling, it's a fair bet that the buds wouldn't form well.  Even mature, well established specimens have struggled in many areas.

If it's doing well now, just remove those dead/decayed buds, and keep it well watered over summer into autumn, if there are more long dry spells. A mulch of bark, or good compost, after watering will also help preserve moisture. 

sarahgrahame

Thanks Fairygirl. I didn't realise the buds formed many many months earlier! Fingers crossed for next year then. This plant is of great sentimental value, so I really want to get it back to full health.

Fairygirl

From what I can see of the rest of it, it looks healthy, so I can't see it being a problem in future. 

Lyn

As it’s bare in the middle with just leaves on the top I would cut it right back, give the roots a chance to recover, they soon grow back, and it will shoot out all along the stems and make a nice thick bush.
I think they’re pretty well finished once they’ve gone bare like that, not pleasing to the eye. 

Fairygirl

Yes - I forgot to mention that. Lyn's right - they respond well to a good haircut 

sarahgrahame

Thanks! When's the best time to give it the haircut? And how ruthless should I be?! What sort of height should I aim for?

The bush is no more than a metre tall and a bit more than that wide, at the moment. The left hand side isn't too bad, but the right hand half is very sparse indeed. The light's wrong for a photo at the moment, but I might pop back with one.

sarahgrahame

I'm back. See how dead looking the branches to the right of the picture (the middle of the plant) are? And the ones on the right have leaves only at the very top. So I can't prune to leave any foliage behind.

Advice on how to do this would be so appreciated. You can see the remains of the damage from last year. Every leaf had that brown tip this time last year (or at least the ones that weren't dead, did!

JennyJ

If it were mine I'd take a chance and cut it back hard, maybe to 6 or 8 inches from the ground, then water enough to keep the soil damp.  Kill or cure! (Background: my garden is small, no room for things that don't pull their weight so if it didn't recover well I'd put something else in the space).

sarahgrahame

In very tempted to prune it right back but killing it isn't really an an option, as my daughter and my late husband bought it together during the later stage of his illness. So it means a lot to us, and especially to her. 

I'm guessing there isn't really a half way house on this, between leaving it alone and risking its demise?

hogweed

Actually there is - you could prune back the back half and then see how it goes next year. If it is a success, prune the front half next year. I would take it back to maybe half its height at the back. Anytime now.