I've spread Anemone nemorosa around many beds from just a few of the tubers/rhizomes, and found them very easy to dig and spread in late summer, since they are ephemeral and go dormant below ground when the dry season begins in July, until late winter when they wake up and spread like wildfire. But Anemone japonica/tomentosa require a different technique. I found a good website about taking root cuttings, and dug a few clumps in March, then transplanted the main stems with roots to various places around the garden, and cut 2-3" pieces of root and put them horizontally in the top of some 4" pots in potting soil, peat moss, and perlite, my standard transplanting mix, and covered 1/2" deep, which I then kept on my east-facing concrete porch, which moderates the temperature in winter, acting like a heat sink. For a long time I didn't see any results, but tiny plants began to emerge, and here they are now-
Also in front are a couple of rose cuttings I made last fall that rooted from Madame Plantier, a most exuberant OGR that I obtained from a rooted cutting myself. It was the only one of 6 roses that survived the rooting process, which included using dry powdered rooting hormone and a plastic tent with occasional misting.
But, back to the Anemones, I will try to get them planted out, like most of my other plant starts, in the next couple of weeks before we start getting hotter and drier weather, and hope they will grow.
Here is a list from the above website of other perennials also amenable to root cutting propagation-
"Here's a list of perennials that are suitable for propagation by root cuttings:
Acanthus, Anchusa, Anemone japonica and A. tomentosa, Catananche, Crambe, Eryngium, lardia, some Geraniums, Papaver orientale, Phlox paniculata, Pulmonaria, Pulsatilla, Stokesia, Symphytum, and Verbascum."
Some of these like Symphytum I just divide in spring, Pulmonarias and some hardy Geraniums self-sow well, others I haven't grown or tried out yet.
They do need a moderately cold place to root, like a cold greenhouse, cold frame, or my front porch.
Spring is almost over, so Happy Summer! -Hannah