Why are my rhododendron leaves turning brown?

~It doesn't look too happy! I wouldn't use tap water at all if you can help it and what ratio white vinegar did you use?
This info is from another site:-

Rhodies do need plenty of water, especially in hot dry weather and
when they're in full growth. When you plant them, dig in plenty of
organic matter such as leafmould, compost from your own heap or peat
if you have neither of those. This will help retain moisture in the
soil, as well as restoring some life to it to make up for the ravages
of the Leylandii. Remember they like acid conditions, and most general
purpose composts from garden centres are slightly alkaline. The
exception is ericaceous compost. Don't plant them any deeper than they
are in the pot when you get them, and after planting give them a good
thick mulch of leafmould or peat, but if your own compost contains a
lot of soil, I wouldn't use it for mulching. The mulch must be coarse
to let the rhodie roots breathe. Some shade is also a good idea, but
if you've recently removed some leylandii, I don't imagine there'll be
much of that.

Newly planted rhodies should be watered in well, and will require more
attention in their first season than well-established rhodies. Rhodies
that are suffering stress due to drought will show it by wilting, but
ideally you should get them watered before that happens. In really
hot, dry weather I would water at least every ten days. Spraying the
foliage in the evenings is also a good idea, especially if the soil
appears moist but the plant is still wilted. Remember to use acid
water, preferably rainwater as tap water is often treated to make it
alkaline, if it's not alkaline naturally. If you can't get enough
rainwater and your tap water is alkaline, add a couple of cc of
vinegar to each watering-can, but no more. A peat mulch can form a dry
crust that sheds water and stops it reaching the roots. In this case
lightly disturb the mulch with your fingers to break up the crust
before watering, but don't poke too deeply with e.g. a hoe as you'll
damage the surface roots. Adding a few drops of detergent also helps
the water to wet and penetrate the peat.

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I suspect they did not get enough water when we had the two week heat wave. Also what is the soil mix in your raised bed?

Thanks for your responses.

I didn't realise they needed quite so much water. Because they are hardy and no obvious evidence of wilting, I presumed they were OK on that front, even in the dry spell we had, but I think that might be where I have gone wrong.

I'll stick my head on the line and say that I am a novice gardener and fairly new to the joys. However, the soil mix is comprised of quite gravelly soil, which was there originally, mixed with lots of ericaceous compost before planting. Added more recently was some Miracle-Gro slow release ericeaous pellets, which it says on the pack incorporate during March to September at three month intervals.

Getting the right type of water is a problem. I don't have a water butt and nor do I have the room for a water butt, so I cannot collect rainwater. So, when it's dry I have to use non-rainwater methods. It seems the method with the vinegar is OK, but I think I just have not been doing it enough.

Do you think I can make the plant recover? I really like rhododendrons!

Are you sure that you can't collect some rainwater in a container ~not necessarily a water butt?
Recently I purchased a butt which fits flat against the wall and fits under the down pipe from the roof~it doesn't stick out very far~admittedly not as cheap as the normal ones but worth it as it can take up so much less room.
If you were to put your plant in a pot containing ericeaeous compost for a while could you stand it where it would get the maximum rainfall?
I know that rain doesn't fall conveniently into a pot but the foliage would get wet.
I think it will recover over time as long as you watch the watering.
I have a standard holly bush which got very poorly being watered with tap water when I ran out of rainwater but was totally rejuvenated by putting it into a large pot of ericaeaous soil.
You can buy pure water~not de~ionised from a pet shop dealing with fish.
Our local one sold me a container and about 15/20 litres of water for about £13.50 but you can go back and get the container filled for about £4.
I grow protea which can't have tap water at all and recently had to find alternative sources when my water butt ran dry so I do appreciate your position!
Best of luck!
Arlene

It really depends where you live whether using tap water is going to affect your plants. If we have to water the veggies. or the alpine garden using the sprinkler we obviously use tap water and have never had a problem. But our water comes from bore holes near the river Spey and is only lightly treated.

~our water comes from the Llyn Briane reservoir from possibly limestone hills as it seems to be very unkind to acidic loving plants.~

Yup that would be a problem Arlene, it all depends where Manwithspear lives...

I live in Essex and, yes, the tap water is heavily treated and very hard.

I was using brown vinegar, rather that white. As for the quantity of vinegar I was adding about a tablespoon to a 5 litre can.

I suppose the oddest thing is that the rhododendron next to it is doing fine, albeit it's not the same variety.

Thank you for your comments - very helpful.

~I hope it recovers quickly for you~if you have a downpipe anywhere that you can get some rainwater from and store it in anything at all~any shape cheap plastic container?
then that would be a help.
It would be nice to know how you get on,
Best regards
Arlene

ello Cuz, glad that you are finding your way around GOY sorry taken so long to reply on here, not been on for a few days.... mmmmm you know what i have had something very simular on 2 of my Rhodo's, and like yourself have others growing around it that look fine... the one in the front garden has had it, had to dig it out and dispose the one in the back seems to have picked up ok... i am thinking one of two things wronge with mine.... 1) virus 2) too much sun.... in my front garden it gets it all day... and i think the brown splotches i had were proberly due to scorching... this may sound obvious but what time of day do you water Andy? obviously should never water in full sun... it could also be dehidration.... what you have'nt mentioned is that you live on the cost Andy... i am wondering if this could be anything to do with it too? i know that you have one that is ok near it but this is well established, it may just be wrong time of year to plant and needs some time to get going?... i know a couple of very good plant experts on here.. i will go and draw thier attention to this question....... back in a bit xx