Amy: Instead of mulch (woodchips) just buy many bags of a quality black topsoil (manure/compost) and use a lot of it on your plants. What do you mean by the ground is concrete? No ground is concrete. Anyway, you can reuse your compost/manure topsoil mix for the transplant in the spring. A lot of people lay a patio tree rose down and cover the whole thing (top and all) up for the winter and they survive well. You might do well to just call a nursery and let one of their guys come out and do it for you. I see you have a lot invested in a few plants. Why not spend a little more and be safe.