Posted: 03/01/2014 at 20:55
Hardwood cuttings at once, if not sooner.
If you click on 'how to' at the top of this page there's an article on hardwood cuttings. I often put them in pots because I never have a suitable bit of ground ready but I should think in the ground would be better.
My physocarpus is in some shade, maybe too much of it. It gets some die back on new shoots sometimes though overall it does OK