Answer: You may be able to maintain them by frequent -- but light -- pruning. Trim back individual longer branch tips. Cut just outside a side branch. Be vigilant about pruning because if allowed to become overgrown, they will not recover from a hard pruning that reveals bare wood. Late winter is the best time to prune these. In the long run, you may find it preferable to replace these with something that matures to the desired size.
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