I cut into woody stems. If they have buds/sprouts, will grow from there; if not, stem is probably dead and should be removed anyway. Same with lavender, which I never understood -- you can't hurt dead, and if not dead then it's going to sprout.

Lots of plants will not generate new growth from bare wood so be cautious of blanket statements to the contrary :) Evergreen woodies or subshrubs - like lavender or heathers - are particularly sensitive to this treatment.

Caryopteris is a true woody shrub in my climate and only gets a trim of tip damaged stems or obvious deadwood. I cut back Russian sage by about half, only because it grows rampantly and gets too floppy if not reduced in size each season. Culinary sage is an evergreen shrub and doesn't require pruning other than snipping off new shoots for use in the kitchen. Other salvias may or may not be cut back depending on their habit. Most of the ones I grow are also woody subshrubs and get minimal trimming.

Hmm. Well I just cut off a lot of perfectly good wood! I assumed that cutting back was to stimulate a fuller form. Should it be treated more like spirea, eg taking out 1/3 of oldest stems each year or periodicaly stooling it?

Caryopteris is one of those plants that is temperature sensitive and will act as a herbaceous perennial in colder climates while remaining a smallish woody shrub in milder climates. I would guess that in upstate NY it is more a dieback perennial than it is a shrub and so would benefit from cutting back. Somewhat similar to buddleia in that regard :-))

I am in the nyc area (xone 6b). It’s not a herbaceous perennisl here, at keast bot every year. So if I might repose my original queston - can i safely cut back thick trunks?

Sorry - thought you were further north :-) You can cut back if you want to (if your climate and winter don't do it for you). Or not. It's your choice.

I do cut mine back every few years just to keep it tidy and size in check but I never have cut back very hard. No more than a 1/4 to a third of the total plant volume.

"So if I might repose my original queston - can i safely cut back thick trunks?"

Yes. From a zone 5'er.

Thank you to the Forum for this timely post. My caryopteris had no die back so it only received a light trim yesterday to shape it.