Cut a length of poultry wire that is wide enough to surround the exterior of the strawberry jar with 2 to 3 inches of space between the wire and the jar. Secure the ends of the wire together with plastic zip ties to create a cylinder.
Place the poultry-wire cylinder around the jar. Anchor the bottom of the cylinder to the ground with stakes if it is taller than the strawberry jar.
Fill the cylinder with clean straw, packing it loosely around the sides of the jar. Cover the top of the jar with a 2- to 3-inch layer of straw. Straw insulates the strawberries and protects them from frost damage.
Remove the straw in spring when new growth appears on the strawberry plants. Keep the cylinder in place and the straw nearby so you can quickly recover the plants in the event of a late-season frost.