Preparing Vines For Winter
Assuming you've chosen the hardier varieties, you'll find them surviving well under winter conditions. To help them, don't add any fertilizer after mid-summer. You want new growth to slow down and any wood that's around to toughen up before serious cold arrives.
Keep watering your vines, though. They are still using their roots to store energy for the winter.
After the ground freezes to a depth of 2-3 inches, apply a thick but lightweight mulch of straw or small evergreen boughs to help prevent the repeated thawing and refreezing that can heave up roots.
Finally, the next time you plant, choose protected sites where the vines will not be subject to drying winds or direct southern sun in winter. Avoiding the sun sounds strange, but hot bark splits when cold nights arrive.