|Is it OK to prune my cleyera in half (top and sides)without damaging the plants?|
Yes it is okay. The best thing is to leave some foliage, that is don't prune back so far the plant has no leaves left. This may mean pruning half to two thirds of the shoots back initially and then when they start to sprout, prune the others back. It will look bad for a time then start to resprout new growth.
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