I am trying to get information on the proper time to prune my photinia hedges. I am located in Western Oregon where we periodically have freezing temperatures from November through February. Especially in December and January. I have one researched one site that says to prune in the dormant winter months. Another says to prune no later than the end of August if there are freezing temperatures expected. I am currently and have for several years been fighting black sport disease. The plants typically look great through the end of March and are a bright red for a short time. Then the black spot disease appears and my 5 hedges get infected to various degrees. What do you suggest?
Prune after mid august.
These links will help you.