Mulch helps regulate soil temperature and prevents repeated freezing and thawing which can heave plants right out of the ground. This can be damaging to the plants and can result in death. By this point in the year we have already had several days of low temperatures and it is likely safe to go ahead and mulch strawberry plants.
Straw is the best option for mulch in this case. Apply three to five-inches of straw over the plants using a wire or plastic fencing to hold the straw in place if necessary. Strawberries grown in raised beds need a few extra inches of mulch since they are not as well-insulated. Container-grown strawberries will not likely survive our winter if left outdoors. Consider bringing the container into a garage or shed for protection through winter.
In the spring as new growth appears, remove the straw a little bit at a time to re-introduce the plants to the elements. Make sure the temperature is above 32 degrees F to avoid damaging new buds. A light layer of mulch can be left in place to keep the berries off the ground and to help retain moisture in the soil. (Cynthia Domenghini)