I have several holly bushes in the front of my house. I don't really know what type; however they are what I would call a "normal" holly tree (bush). Very pointed leaves and green berries. They are very tall and I would like to cut them way back. I have been told that I can trim them 2 feet off the top and 1 foot on each side; and was told they would grow leaves back. Do you think this trimming is too severe or will it be O.K.?