At the end of last year, I potted some black raspberry canes. Some were from canes that I stripped and put in potting soil, others were from tips that buried themselves in the ground. Right now I have them in our sunroom and they look healthy and green, although I do need to transplant into larger pots. They are about 5-6" high. Should I let them continue to grow over the winter, or do they need to be in the cold to die off and regrow in the Spring? Is there anything special I need to do with them before transplanting outdoors in the Spring?