come late summer after flowering, choose non-flowering shoots of about 3" and dip into hormone rooting powder. should root about 5 weeks or so. pot on and keep in unheated g/h over winter before planting out in the following spring.

also, you can choose the layering method, but i've only done that once many years ago and it was via a pot-to-pot, and i don't remember how long that took but i've still got the plant back then and it's "babies".