Cestrum nocturnum really does not need to be pruned for its own sake. However, it can get leggy and a bit tall in time. Therefore you could do a severe cut back to a couple of feet shorter that you want it to end up. This would leave it a bit ugly for a time but it should quickly regrow and fill in again. Another approach would be to do a light shearing periodically during the season. If you cut the gangly shoots back to just above the spot where a side shoot attaches to the main shoot, it will leave the bush with a more natural, attractive form.
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