when to pot mugho pine? others?
 

I live in NE Ohio. The winter is dragging out but there are hopeful
signs of spring. I have several different varieties of trees planted in
the ground. Should I put them in pots as soon as the ground allows
access?
I've had trouble keeping mugho pines alive once in pots. I've only tried
the garden store variety but I got one last summer that is a dwarf
variety and had already been put in a bonsai pot. I put it in the
gardent to winter over. When should it come out? Do I return it to the
outdoors once in a pot or keep it in until it gets past the freezing
weather? what about a shipaku? Ginko? I don't want to wait until the
weather breaks and then pot, do I? Any advice would be greatly
appreciated.