Answer: You can prune to control the height but this will ruin the natural structure of the tree. It may also encourage sucker growth from the roots. The best time of year to prune poplars is in the early summer or wait until late fall after the tree has dropped its leaves. Keep in mind that these trees grow very tall and tend to be short lived. If it is too large for the space you might consider replacing it with something else that matures to the size you have space for.
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