Berberis dawinii

Hi,
We moved 18 month ago and the 4 berberis are well established trees atop a banking in the garden

Problem is they are very tall and look sparce, wild and have dead sections.

How far back can I prune and if I cut severely will they regrow as bushes and not trees

 

It's a bit difficult to make out the dead bits on the photos supplied. Better and closer photos would help.

 

Hi Nigel...Ive cut the dead bits out but because its so tall there are big gaps at the bottom and there is no shape to any of them..if I cut back to 18 inch or so will they regrow as bushes from the stumps left

 

I don't have specific experience of B darwinii and pruning. I would be inclined to cut one back by about two thirds and if it grows away next spring, then treat the others similarly.