Rooters and runners. A few months ago I potted a sprig of Yellow Archangel and since then it has put out a long runner which will root where it touches the soil. NB this is not the native species of ancient woodlands that goes by that name. This is its vigorous European cousin Lamium galeobdolon subsp. montanum. 

 I dug up some Symphytum ibericum from a patch on the allotment a few days ago to pot up. It spreads in a similarly stoloniferous way. Needless to say these plants make good ground cover i.e. they are invasive! They are semi-evergreen (at least in my neck of the woods) and flower in late spring.