A yard full of fallen dead leaves can appear to some people as being an unsightly mess. To a gardener fall leaves are a welcome helper to the garden. A gardener can find many uses for dead leaves, one being plant protection. Winter crops such as carrots, beets, turnips, and cabbages can continue to grow well into the winter if they are protected from cold temperatures, frost and snow. Once the plants have stopped growing, leave them in the garden, covered with a thick warm layer of mulch to help keep them fresh and crispy.
Well before the first hard frost; ensure that plant roots and tops of root crops such as carrots are covered with soil. Leave the green leaves of the plants uncovered in order for the plants to continue growing. In areas where frosts may come early, cover the plants with old blankets, row covers or straw and uncover during the day when temperatures rise. Vegetable plants accumulate high levels of sugars during cool nights, enabling them to survive cold temperatures and acquiring a better taste.
As winter gets colder and harsher cover rows of plants with a one-foot layer of leaves and straw. The straw will help prevent the leaves from blowing away. In extremely windy areas, put the leaves and straw in trash bags and lay them on the crop rows. Do this before the ground freezes. Depending on the USDA Plant Hardiness Zone for your area, you may need to add a thicker or thinner layer of leaves and straw.
If woodland critters find the leaves and straw to be the perfect place for a winter home, set out some traps between rows to catch them. If you do not want plants to reseed in the spring, be sure to remove them well before spring planting.
Vegetables that can be stored this way in your garden are carrots, beets, parsnips, turnips, celery, rutabagas, cabbages, looks, kale, and spinach.
Leaves and straw can also be used to protect young trees and bushes, especially rose bushes, from cold winter weather. Depending on the size of the plant, use an appropriate size of chicken wire to wrap loosely around the bottom of each shrub, making sure there is at least a 10 to 12-inch open circle between the shrub and the chicken wire. Fill this space tightly with leaves and straw, which will protect the roots and base of the plant.
Source: Personal experience, Organic Gardening