Young Prunus Serrula struggling

Earthling850

We planted this young Prunus Serrula on the spot where a silver birch had blown over in last February’s storm.  It had seemed to be thriving but on returning from a week away, we found this. Is it a result of the hot summer? Under watering? Or a pest?

Fairygirl

Have you got a better pic of the whole tree?
Bits of browning foliage can happen to any tree, at any time, so it's hard to be specific about a cause.
Drought is certainly a major factor for lots of trees, this year and last year, but the size of the tree, the conditions it's planted in, the location, the aftercare, surrounding planting etc, are also factors which can affect them. 

Earthling850

The tree is in the sunny end of our north facing garden. There’s a single cavolo nero plant, some marjoram and a comfrey plant which I keep in check.  Further away are some grasses and verbenas. The grass on
 the left is in a pot. The tree roots are not crowded 

Fairygirl

I think it's probably bone dry, and therefore unable to sustain the foliage. It'll probably recover over winter as long as it gets enough water in the next few weeks.

I can't see the base of it, but if there isn't enough decent quality soil for it, it's going to struggle a bit. Is it a raised bed of some kind? They drain much more quickly too. 

BobTheGardener

Most likely lack of water.  Trees planted at that size need a couple of buckets of water a week from planting until the leaves have fallen in autumn as it takes them a lot longer to grow roots out into the surrounding soil to take up food and water (younger specimens establish more quickly.)  For the first year, you need to treat them as if they were still in the pot.  Give it a good drink until winter and it should come good next spring but do water it throughout any dry spells next year.

I would also strip off the bark of that piece you removed for the first photo and look for any staining of the wood below which could indicate a soil-borne disease.  I mention that because it's possible the silver birch had some kind of root-rot like phytophthora which weakened them, leading to it being blown down.  Fingers crossed it is just the effects of drought though.

Earthling850

Thank you both for your help. I suspect too that it’s too dry. I’ll do what you suggest Bob and keep well watered. Is it worth mulching around it with garden compost too ?  I’ll also check for disease.  Thanks again 

Obelixx

Mulch will help but only once the soil is throughly wet after several waterings.  Otherwise you'll lock in dryness.