Putting the garden to bed for the winter is mostly a matter of cleaning up and covering up. As fall progresses and temperatures drop, those plants that aren't killed outright by frost prepare for dormancy. Clear out the blackened stems and foliage of annual flowers and vegetables to prevent the possibility of their harboring disease pathogens and insect eggs over the winter. The cool weather is a good time to make a cold frame, dig and box in raised beds, and make general repairs.
While it appears as if all activity in the garden has stopped, there's a lot going on under the soil until it freezes. Newly transplanted trees and shrubs, divisions of perennials, and hardy bulbs are all growing roots, drawing on soil nutrients and moisture around them. Earthworms and various microbes in the soil are still processing the organic material they're finding. Most likely, the organic mulch you spread to protect the soil during the summer months has substantially decomposed. It's important to spread new mulch now -- a thicker winter layer -- to protect plants and soil over the winter months. The idea is not so much to keep the soil warm as it is to keep the temperature even. Once the soil is frozen, mulch keeps it frozen. So if you have shade trees, convert the fallen leaves to mulch and use it throughout your property.
Snow both protects and endangers plants. A good snow cover insulates the soil like a mulch. However, snow piled on evergreen branches weights them down, risking breakage. Knock snow from the bottom branches first, then work upward. This way snow from above will not add weight to the already burdened lower branches. If branches are bowed by ice, don't try to free them. Instead let the ice melt and release them gradually.
- Cut back dry stems of perennials to soil level after frost to neaten the garden and remove pest eggs and disease spores that may linger. Leave stems with attractive seed heads for winter interest.
- Compost dead plant debris to create an organic soil conditioner. Hot, active piles kill weed seeds and disease pathogens; passive, inactive piles do not. Throw questionable plant material in the trash.
- Cut off diseased foliage from evergreen plants and shrubs and discard it in the trash. Rake up and discard the old, disease-bearing mulch, too.
- To prevent rodents from nesting in the soil, wait until the ground freezes before adding a 6-inch layer of organic material as winter mulch.
- Mulch perennial and shrub beds with pine needles or chopped leaves. This protects both plant roots and the soil and moderates the effects of extreme temperature changes during winter freezes and thaws.
- Mulch bulb beds with evergreen boughs to protect the soil from shifting and cracking during the winter. Otherwise plants, especially small, shallowly planted bulbs, can be heaved to the surface.
- Protect the tender bark of young trees from gnawing critters by wrapping stems or trunks with wire or commercial tree-guard products.
- Screen evergreens, particularly exposed broad-leaved types, from drying winter wind and sun by setting up burlap screens or shade cloth shelters.