It is October 10th. I have a hedge of Thuja Occidentalis Pyramidalis on central Vancouver Island. The individual plants range from 8 to 10 feet high. I would like to level the top of the hedge to 8 feet. Can I trim the hedge plants down by up to two feet this month or must I wait until the hedge goes dormant - or what? We haven't experienced frost yet in this area and may not until November.