Trees in fall are in a state of serious change and reorganization. The tree is becoming dormant. A tree heading toward winter will sense the changing temperature and light and obey the dormancy controls built into the leaf. Trees may look inactive going into winter but the fact is they continue to regulate their metabolism and only slow down some physiological activities. Trees still continue to slowly grow roots, respire and take in water and nutrients. Winter is a difficult time for a tree. A dormant tree still needs to be protected (winterized) to remain healthy and free from diseases and insects. Winter weather encourages destructive pests to snuggle in and wait for spring to revive their destructive lifecycles. Small investments in your time can pay off big come spring.
Prune dead, diseased and overlapping branches in late fall. This will form and strengthen the tree, encourages new strong growth in the spring, minimizes future storm damage and protects against overwintering disease and insects. Remember that dormant pruning has another benefit – it is easier to do during winter dormancy than in spring. Correct structurally weak branches and limbs. Remove all dead wood that is clearly visible. Properly prune branches that can touch the ground when loaded with rain and snow. Foliage and branches that are in contact with soil invite undesirable pests and other problems. Remove damaged and declining twigs, branches, and bark or any new sprouts that have grown at the tree base, or along stems and branches.
Dry spells in winter or hot daytime temperatures will desiccate a tree very quickly. Watering may be needed where soils are cool but not frozen, and there has been little precipitation. Winter droughts need treatment with water the same as summer droughts, except it is much easier to over-water in winter.
A dormant spray may be a good idea for deciduous trees, ornamentals, fruit trees and shrubs. This should be done after pruning. Obviously, you will lose much of your effort and expense if you cut off treated limbs. Choice of chemicals is important. Dormant sprays include lime, copper and sulfur combinations to kill overwintering microorganisms. Dormant oil controls insects and their eggs. You may need several types of sprays and oils to be effective.