Sorbus tree

Our clay never dries out to any great extent here, but the point about clay, as I said a month ago, is that for successful growing, it needs amended to help with drainage in wet areas, and to help retain moisture in areas which can have little to no rain for weeks on end.
It's always false economy to plant in to unamended clay, regardless of the plant.

 

I am in the North East too and our Rowan tree is the same. Ours has fruited so early on that most of berries are spent or on the ground and we are beginning to lose leaves after they started " turning" really early. I used to enjoy watching the blackbirds eating the berries off the tree during November in earlier years. Have cared for it as recommended and never had this problem before but we think it's been the odd weather patterns we've had since last winter here. We are hoping it will be okay next year.