Pruning Photinia

Nick Leonard asked 4 years ago

I am growing a hedge with mixed Portuguese Laurel and Photinia, and haven’t touched them for the first couple of years to let them get established. They are slow growing and most of the Photinia are bare on the lower parts and there’s a few tall ones with growth at the top and bare branches. To make them thicken out, should I be pruning back to ground level? When should I do this?