Caryopteris cuttings root very easily from internodal cuttings with greenwood or semi-ripe wood. I haven't tried hardwood cuttings of caryopteris so they may root well too, I just don't know. I'll try it this fall and see what happens.
Here's how to take caryopteris cuttings:1. Take a stem-tip cutting just above a node.
2. Leave a pair of leaves on the cutting. The leaves were the only node I left on the cuttings. Two or three node cuttings may make a more established plant faster but I was looking for quantity rather than size.
3. Treat the cuttings with rooting hormone. You don't really have to do this (for caryopteris) but I've found that it speeds the process up.
5. Wait 7-10 days and check for root resistance by gently pulling on the stem.
That's all there is to it, very simple. You could even try just sticking the cuttings in the ground to get more plants but with the June heat already here it's safer to bring the cuttings indoors to root.
I'm currently working on getting more 'Powis Castle' Artemisia to root. I managed one already but it is such a great foliage plant that I can't stop with just one! Hopefully I'll have a post to share on that soon.
Quick Propagation Tip: June is a good time to take crape myrtle cuttings and to start taking cuttings of asters and chrysanthemums (mums) for fall! Just take your pinched off mum leftovers and treat them like the caryopteris cuttings in this post.
For more propagation fun check out some other handy plant propagation posts!