Sorry 'Nelly' I can't help with the expert advice, but will tell you what I know. I just put mine straight into the garden, so can't tell you which medium would be more suitable, though I suspect a reasonably well-draining potting mix would be the shot, or a propagation mix.

The pieces will grow, whichever way you plant them, though I found that laying them flat on the ground encouraged them to send up new shoots from many of the nodes.

Hope this is of some hellp to you.

I discovered by accident (having cut some flowers for the house one year) that the stems root very easily in water, and can be potted on later. Just trim back some of the longer leaves. Have never grown them by laying down but I suspect they would root just as well in any growing medium.

Thanks Liatris and Alison.

I am sure both of you are more expert than me.

I will try both ways seeing I have two pieces.

ps Just noticed my lousy spelling on my first message.Sorry, must have been in a hurry to get back outside to my garden . LOL