Hi I have a thuja occidentalis hedge that is 8 feet tall . It has been planted around 20 years ago ,pretty closed together ,1-2 feet apart. The hedge is 4-5 feet wide. The previous owner has always pruned it pretty square so the top is flat and during winter the snow accumulates there . Is it possible to prune it so that is will grow taller. In my dreams I would wish it would grow to 16 feet but maybe that's impossible once it has been 8 feet for years. Is there a way to prune it so it will grow tall? Should I just not prune the top anymore ? or prune a little and eventually it will grow more tall year by year? or should I try to pick a leader branch on each plant and prune it in a special way? Any advice would be welcome. Thank you
Yes, it will grow taller, if left untrimmed. The risk is that several erect stems will grow from each plant in positions where they are not very straight with respect to the original stems, i.e., have kinked and forked stems from the base to the top. That is a recipe for snow breakage in the future. The best thing to do is therefore select the new leaders which are straightest above the original trunks, keep those, and prune out others. It will look gappy at the top for a few years as a result, but side shoots from these will eventually fill in the gaps.