Maybe grow tropicals and bring them in for the winter? (Lemon, hibiscus, lime, ficus, etc.). I think the roots are probably freezing in the containers because they're much more exposed than when the plants are in the ground. My deciduous trees and shrubs are in the ground, but I have several tropical trees I bring outdoors in the spring and inside in the fall. (I live in NJ.) Lemon trees are especially nice...they're small, bloom in winter (the smell is fabulous) and they give you fruit.

Regarding a ground cover for shade my favorite has been sweet woodruff. I was surprised some people thought of it as invasive. It grows at a nice speed and has very shallow roots so I can pull out a chunk easily. Very well behaved in my garden. I am in the PNW so I'm not sure how it is in your area.

Have you tried contacting your local Master Gardener program for information? They will be familiar with your local growing conditions.

Pennsylvania Master Gardeners

re the maple dying.. sorry to hear that. We (in Ontario, Canada) did have a harsh winter but all the neighboring Japanese maple (bloodgood) survived with ease. I think it was the combination of warming and freezing that killed it and possibly most of your container plants. You should consider planting it again but this time locate a place where it can be protected and mulch heavy to prepare for winter. Containered plants would not survive winter too long. Youd have to insulate the containers in order to help keep its temperatures steady. Above ground plants will experience temps far colder than inground plants. So if you wish to continue with above ground plants, insulate it well. Get haybales and place the containers within and cover the bottom up with hay or other forms of mulch. That guarantees survival.

I second the sweet woodruff (smells great!) although you may have trouble if your shade area is dry. Other shade groundcovers: foamflower, vinca minor, pachysandra, and for a very bright look, creeping Jenny (also in Zone 5b.)