"Evergreens" covers a lot of territory. In addition to the foliage dessication you are in consideration of, there is also a root cold-hardiness issue as well as root dessication protection that will be needed.

I think your best bet is to site the plants together, so they act as their own wind-break. Then, I would mulch very heavily with wood chips from recently chipped live trees. The compost heat will help to moderate the (cold) effect of the plants being sited above ground. Then, I would wrap the perimeter of the "grove" with burlap to slow water loss from foliage. You may wish to consider several (probably 3) applications of an anti-desiccant like Wilt-Pruf.

It would have helped to know the # of plants, the size, the genus/species. Some evergreens are hardy enough to withstand the chill, but dessication would still be at issue; so even the more hardy plant materials would benefit from the mulching. Don't forget to water or throw snow on the rootballs as needed.

Al

I have overwintered some evergreens such as White Pine, Fir, in black nursery pots. Put them in an area sheltered from direct wind, they did just fine.

Did you note the trees are b & b?

Al

Once the ground and rootballs freeze, don't water any more, only do it if or when there's such a long thaw that they actually start to dry out a bit. The danger in MI is that you could get some spring thaws followed by refreezing, and that's what you need to mulch very well against.