Fall is the best time to prune deciduous trees and shrubs, as well as planting new trees and shrubs. During the cooler weather, insects and disease are less of an issue, and without the leaves, it's easier to see which limbs need pruning. Cool weather allows new plantings to spread their roots in cool moist soil and the plantings experience less shock in the process.
As the colors of fall come to a close and the leaves fall and scatter - plan ahead and protect your plantings from the cold northeast winters by winterizing them with mulching. Protect your plants with a layer or mulch 2-3 inches deep, leaving a little air space around the base of the plant. You can use purchased bark mulch, or create your own with a chipper. Anything organic, such as leaves or branches, can be used as long as it is disease free.
If you do have any diseased leaves or stems, it's important to remove them so that they do not re-introduce the disease in the spring.
Once the snow begins to fall, the snow will naturally provide an insulating blanket to protect the plants. However, if there isn't any snow, plants can be exposed and vulnerable. With a little fall effort and planning, mulching can protect your planting investments.