You could try basal cuttings or division, i do basal cuttings in the spring, very easy.

My Ragged Robin are loaded with seed which I've been collecting .... another propagation option.

I have a lot of lychnis coronaria around the garden. I started with a few plants given me years ago by a friend and they just self-seed themselves around. I wouldn't be without them and if they come up somewhere inconvenient I just pot them up and give them away. I have divided one or two in the past but have never taken cuttings . I don't know lychnis jenny though. It will be interesting to hear how you get on with them.

Sorry Jenny,
I wasn't being funny--have just realised 'jenny' was a signature!