Last week I got some kerria japonica for my woodland garden and the owner of the nursery(he is a very well respected horticulturist in the county) says they will benefit if cut back hard as soon as they finish blooming to encourage more growth that will likely be bigger than if you hadn't cut it back and they grow. I always thought plants should establish first or at least settle into their new spot before touching anything of it? I asked him regarding this but he said no need to wait and do it right away. Or will the rapid new growth also allow the roots to grow into the soil better?