Answer: Those directions are for Caryopteris being grown in a much warmer climate than yours. Caryopteris is grown as a dieback shrub in Illinois, so I would not prune it at all right now. Wait until spring, then trim it back to remove winter damage. (This may mean cutting it back as far as the ground.) You can also trim it to be fairly symmetrical at that time; you want to take it back to about a third of its height. This will stiumulate branching and help keep it dense. I would not trim it now as this would stimulate late season growth and this would result in additional dieback this winter.
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