Answer: This arborvitae (Thuja occidentalis) grows about fifteen feet tall and only three or four feet wide. The natural growth pattern is tall and narrow or columnar which is what makes it so good for a hedge. (They grow their best in full sun and will naturally be sparse or thin in a shady site.) Trimming would not make them grow thicker, it is just a matter of time waiting for them to mature over the years. I'm sorry I can't be more encouraging.
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