Overwintering Indoors to promote root growth

I'm experimenting this Wisconsin winter by taking some of my young plants--hardy kiwi (Actinidia arguta), wisteria, paw paw, and some others, hoping that the relative warmth indoors helps them develop more before they move to their final homes in the ground. Any hints or advice that will help me?

Hi Douglas, It is common for tree roots to grow at 40F. But the soil should be that warm or warmer before setting the trees out. It seems to me that a very deep mulch in the winter might be the better way to go as you don't disturb the roots with transplanting. Also, try working with plants that adapt easily to your climate. In the 70s I was always pushing the boundaries of sub-tropical edible plants North of San Francisco. I found it too much work and not in the flow of the natural/local environment.