I have successfully grown trees, shrubs and groundcovers. The bad news is that June seems to be the best month. You want cuttings from "newish" growth. Not too new and not hardened. On the other hand, I'm in Zone 7. You may have more flexibility of time.
There are complicated things (like scraping the bark and wrapping it in damp moss). I prefer taking new growth cuttings, dipping the cut ends in root hormone powder, and sticking them in damp potting soil. I have 3 dozen azalea, 4 Knockout rose cuttings, and 4 dwarf butterfly bush cuttings doing quite well that way.
