Miscanthus is about the only grass that will stand up to the ravages of winter (for me) but I doubt very much that it would survive above ground. You need something hardy 2 zones colder than yours for it to overwinter in a container.

Interesting. Structure, even if dead is an option as it looks good with snow on it. I may end up doing Thuja, red dogwood, or corkscrew willow. Cedars didn't survive last year. Thanks.

Unless a very large container, nothing will survive winter outdoors in a container in zone 4!! The soil will freeze solid and the roots will be damaged or killed. It would be best to use the containers for annuals or other seasonal plantings and then in winter, use the cut stems or branches of various conifers or colored barked shrubs - as you describe - to decorate the container for winter.

I think I won't experiment with grasses, except I'd really like Phragmites , only in pots. Doesn't spread by seed and holds up to the winter well and beautiful. Have tried it before. Not common around here and I guess I won't find stock anywhere because it has a bad reputation. Will stick to original alternatives.