Answer: Junipers, arborvitaes and yews can be pruned anytime from mid-April to mid-August. Pruning later would likely leave unhealed wounds that could result in winter damage. You'll want to be careful when pruning your arborvitaes: Evergreens need to be pruned based on the presence of their foliage on the branch. Don't cut beyond the green foliage portion of the branch. If you cut back to bare wood, no new foliage will develop. Instead, plan on reducing the size of your plants over several summers, removing some of the foliage each year. In 2-3 years your plants will be smaller yet still full and green.
Best wishes with your landscape!
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