There are several things you can do to give your wisteria the best chance of survival. The first—and most important—step is to provide a good supply of water during the fall. Dry soil harms roots and causes stress; water will transport nutrients from the soil, increasing the plant’s stored energy.
Next, add an extra layer of organic mulch for the winter (about 15 centimetres deep) even if it seems excessive and is removed the following spring. Mulch will keep the soil warmer and encourage root activity, help insulate during low temperatures and keep soil frozen during winter thaws. Even if the plant dies back to the ground, with mulch and moisture, roots will likely survive and send up new stems in the spring.
To further protect the vine, construct a temporary shelter. Put four stakes around the wisteria and wrap a frost blanket around them; fill with dried leaves. Also consider planting a permanent evergreen windbreak upwind from the wisteria, to further shelter your plant.
Need more wisteria help? Get your fussy plant to bloom with these wisteria blooming tips.