JM cuttings and intermittent misting
I have an unheated greenhouse I use to propagate cuttings. Intermittent mist set to go off for about 10 seconds, every 5 min or so. Shade cloth over the area I do misting in.
Cuttings are taken in early summer, new growth only. I like a little thicker stem, and I try to cut about 1/2 inch below a set of leaves. I used to strip all but two leaves off the cutting, but I found that if I can leave two sets or more, they seem to root better (more photosynthesis). Dip in a diluted solution of Dip-N-Grow.
I have successfully rooted Shishigashira, Glowing Embers, Bloodgood, Seiryu, and Sango Kaku. Glowing Embers is by far the easiest to get the root, and has had the best winter survival rate. Depending on the variety/time of year, I see callousing in a few weeks, and some pretty strong root systems after 8-10 weeks. I always get excited when I can lift a flat and see the root tips poking out through the screening in the bottom of the flats!
I try to keep things as sterile as possible, but I never fail to have some moss/algae grow on the perlite. It is a VERY moist environment. I spray down the area at the beginning and end of the season with a strong mixture of bleach water or hydrogen peroxide. I clean and disinfect my tools frequently.
I used to pot the rooted cuttings up individually, but I seem to lose a LOT over the winter that way (can get 5-15 degrees at nights, even in the greenhouse). This year I kept them all in flats, with 4-5 inches perlite/peat moss/sand mixture, and the survival rate seems to be a lot higher.