The only thing I can spot is some dark marks like bruises on some of the branches. It's probably just die-back but worth checking it's not verticillium wilt.
If it is, then it'll be obvious in the Spring once your tree has leaves. You'll notice healthy leaves going dry and crispy at the ends of branches. If you prune a branch, look at the cut end to see if there's a dark ring inside which is another indicator.
Compost alone isn't enough for a permanently potted plant of any kind. You need a soil based medium, so that the soil holds moisture well enough. Once compost gets dry, it's very difficult to rehydrate again However, keeping the pot up off the ground, as it's on a solid surface, is helpful, because they also don't want to be sitting in wet soil permanently. Ensuring the mix drains well, then making sure the soil doesn't dry out for any length of time [for the reasons given] is important, so I'd agree with @punkdoc that it will likely have suffered last year. I had to keep an eye on all my pots here, regardless of what was in them, and we didn't have anything like the conditions that many people had further south. You can't rely on rainfall either, when a plant is in full foliage. If there's no wilt, as @Pete.8 mentions, then no - there's really nothing you can do to encourage new growth, other than keeping it in a sheltered spot out of extreme weather- ie sun and cold winds. If it's ok, it'll come away again. If it creates some nice new growth and thrives, you could give it the odd dose of seaweed over summer. A mulch of bark is also useful for helping with moisture retention should there be another very dry spell where you are. Apply it when the soil is moist
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
I agree completely with the post from @Fairygirl . In very hot dry weather pots may need watering every day or even twice a day when we have temperatures of 35+
I've received some feedback from elsewhere and I wanted to run it past here.
"The red spots on the branches are caused by fungal infection, Spraying fungicide on your plant will help protect it. Look for products that contain Difenoconazole, Azoxystrobin, Propiconazole or Myclobutanil, as plants can easily absorb these compounds. It's also smart to pour fungicide into the soil near the plant's roots, so Absorb it. After the arrival of spring, it is recommended to spray the fungicide again and spray the fungicide on the leaves."
@Pete.8, is this the fungal infection you are referring to? I have inspected the dead end of the trunk that I have cut and it looks clean and there is no mark however, last summer when it all started going wrong, all of the leaves went dry together and started falling.
Ok, that was savage. My plant is half the size now! Is there any technique I can try to encourage branch growth?
Yes. Time and patience.
Repotting in new compost, same roots, less above ground growth. That should do the trick.
re watering. If you watered it in well, it should not need any extra water until it starts to leaf up. The leaves of any pot grown plant divert the water away from the plant, a tree less than some. Learn to recognise when the compost is getting dryish. Weight is the best indicator. If your compost is open and fast draining, watering every day might be unnecessary but would do no harm.
re red spots. To me they look just like the green bark maturing to red-brown. It sounds like your feedback was from a fungicide salesman.
location: Surrey Hills, England, ex-woodland acidic sand. "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
I think the other advice you've had may refer to Coral Spot which your tree does not have. Was coral spot indicated in the advice you got elsewhere?
I wouldn't start spraying or drenching the soil with fungicide until you're sure what the problem is. I'd suggest waiting until Spring and see how it looks when the tree has leaves.
Poke your finger into the compost a couple of inches and water if it's dry at that depth.
If lack of water last year was the problem then your tree should be OK. If it has verticillium wilt there is nothing you can do about it. One of my acers has had it for 5-6 years - it's still OK but does loose a few branches each year.
Billericay - Essex
Knowledge is knowing that a tomato is a fruit. Wisdom is not putting it in a fruit salad.
I have been reading this topic with interest. I have never done anything to mine except to repot as necessary and to break off those tiny spindly white ends that they seem to develop naturally each winter. At some 20 years old a lot of the branches are old and dead looking, but they still throw out new shoots and full leaves each year giving a lovely overall effect to the trees. I keep them well watered - they have to put up with the hose pipe too as our rain water butts are kept for other plants. Not sure if mine are the same variety as yours @pouryasANCZ44k_ but I do have other younger varieties that I treat the same. Sorry, I was going to post a picture but not being at all techy my laptop is not co-operating.
Posts
It's probably just die-back but worth checking it's not verticillium wilt.
If it is, then it'll be obvious in the Spring once your tree has leaves.
You'll notice healthy leaves going dry and crispy at the ends of branches.
If you prune a branch, look at the cut end to see if there's a dark ring inside which is another indicator.
https://www.rhs.org.uk/disease/verticillium-wilt
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
However, keeping the pot up off the ground, as it's on a solid surface, is helpful, because they also don't want to be sitting in wet soil permanently. Ensuring the mix drains well, then making sure the soil doesn't dry out for any length of time [for the reasons given] is important, so I'd agree with @punkdoc that it will likely have suffered last year.
I had to keep an eye on all my pots here, regardless of what was in them, and we didn't have anything like the conditions that many people had further south. You can't rely on rainfall either, when a plant is in full foliage.
If there's no wilt, as @Pete.8 mentions, then no - there's really nothing you can do to encourage new growth, other than keeping it in a sheltered spot out of extreme weather- ie sun and cold winds. If it's ok, it'll come away again. If it creates some nice new growth and thrives, you could give it the odd dose of seaweed over summer.
A mulch of bark is also useful for helping with moisture retention should there be another very dry spell where you are. Apply it when the soil is moist
I live in west central Scotland - not where that photo is...
"The red spots on the branches are caused by fungal infection, Spraying fungicide on your plant will help protect it. Look for products that contain Difenoconazole, Azoxystrobin, Propiconazole or Myclobutanil, as plants can easily absorb these compounds. It's also smart to pour fungicide into the soil near the plant's roots, so Absorb it. After the arrival of spring, it is recommended to spray the fungicide again and spray the fungicide on the leaves."
@Pete.8, is this the fungal infection you are referring to? I have inspected the dead end of the trunk that I have cut and it looks clean and there is no mark however, last summer when it all started going wrong, all of the leaves went dry together and started falling.
Yes. Time and patience.
Repotting in new compost, same roots, less above ground growth. That should do the trick.
re watering. If you watered it in well, it should not need any extra water until it starts to leaf up. The leaves of any pot grown plant divert the water away from the plant, a tree less than some. Learn to recognise when the compost is getting dryish. Weight is the best indicator. If your compost is open and fast draining, watering every day might be unnecessary but would do no harm.
re red spots. To me they look just like the green bark maturing to red-brown. It sounds like your feedback was from a fungicide salesman.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
I wouldn't start spraying or drenching the soil with fungicide until you're sure what the problem is.
I'd suggest waiting until Spring and see how it looks when the tree has leaves.
Poke your finger into the compost a couple of inches and water if it's dry at that depth.
If lack of water last year was the problem then your tree should be OK.
If it has verticillium wilt there is nothing you can do about it.
One of my acers has had it for 5-6 years - it's still OK but does loose a few branches each year.
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
Sorry, I was going to post a picture but not being at all techy my laptop is not co-operating.