Conditioning Your Garden in Winter by Stephanie Suesan Smith, PhD, Master Gardener.
Although most people do not grow vegetables over the winter, you can still work to make your garden the best it can be next spring. First, remove all of the old, dead plant material. If the plants were healthy and died of heat or frost, compost them. If they had diseases or severe pest problems, it is best to throw the plants into a bag, seal the bag, and throw them in the trash. If you compost diseased or pest ridden plants, you can spread the problem throughout the garden when you use the compost.
Till all of the mulch and other organic material into the soil. Mulch will provide a hiding place for bugs over the winter. Tilling it under prevents them from having a place to hide, while enriching your soil with the extra organic matter. If you till a great deal of mulch under, sprinkle some nitrogen fertilizer on it and till that in as well. This keeps the microbes that break down the mulch from depleting the nitrogen in your soil.
Cover crops are plants such as rye and vetch that fix nitrogen and enrich the soil. They also hold it in place during the winter rains. Cover crops keep the rain from washing away your topsoil. They also prevent the wind from blowing it away. Cover crops are generally planted after the garden is finished. Since it has been so mild this year, you may still be able to plant one and get a good covering of plants. In the spring, when it is time to plant, you simply till the plants under and use them as green manure. They slowly decay and release their nitrogen to the vegetable plants you have planted.
If you do not plant a cover crop, you can still cover your vegetable plot to protect your soil. You can spread a three to six inch carpet of dead leaves on your vegetable plot. It is better if the leaves are chopped up such as when they have been run over with a lawn mower. However, whole leaves will work fine. These leaves will gradually decay over the winter. This adds organic matter to the soil, making it rich and productive. Any leaves that are still around in the spring when it is time to plant can simply be tilled under.
A few hours of preparation now will result in fertile ground that is rich and will easily grow vegetables. Spend the hours now and benefit in the spring.