I live on Lake Erie in Ohio. I have plants that are considered perennials in southern zones (angelonia and some grasses). Is there a way to preserve these plants through the winter?
If they are in pots you can move to a sheltered area, like a garage.
If you planted these plants in the ground it is not likely they will survive a winter.
A plant like Angelonia is hardy in zones 9 thru 11 and even covering and mulching will not be enough for the plants to survive.
Occasionally we can cheat a plants hardiness but the likelihood is slim.