My swamp cedar hedge bought at a nursery ten years ago has grown at least twelve feet high. It is in dry clay soil in full sun. Caledon area just north of Toronto. It looks beautiful to me as I love the privacy it provides. My lot is 50 wide by 150 deep so big enough. My concern is that it might start to thin out and we would lose our privacy. Is it wise to trim the top or can we leave it natural? And just prune sides to promote growth at bottom six feet or so.
Thank you for contacting the Master Gardeners of Toronto. Judging from your message, you are doing everything right! By the sound of it your Swamp or White Cedar, Thuja Occidentialis is thriving despite its dry clay location. It is a good idea to tip your cedars lightly at the top to allow more sunlight to reach the lower branches,however please tread lightly as cedars will not put out new growth from old wood.
We do get many questions about pruning Cedars at the Master Gardeners, here is a link t0 our webpage where you can enter cedar in the find it here box.