By Kim Coder
University of Georgia
Trees stand in the face of cold, drying winds, ice storms and deicing salts. Food reserves must be carefully conserved for the coming needs of spring. Water continues to escape trees. Any creature needing a winter meal nibbles on resting buds and twigs.
Trees stand alone against all circumstances that winter can generate.
Winter also is a time of serious change and reorganization within a tree. Many trees won’t survive to grow in another spring. You can do little things to make trees more effective and efficient at surviving a hard winter. A few small investments now can pay off in a large way, yielding a healthy, structurally sound tree.
The "Big 8 List" of things to do to winterize your tree:
1. Remove or correct structural branch faults and deadwood that are clearly visible. Make small pruning cuts that minimize any exposure of the central heartwood core.
2. Properly prune off branches that will touch the ground when loaded with rain and snow. Foliage and branches that are in contact with soil can invite pests and problems.
3. Remove damaged and declining twigs, branches and bark. Don’t leave pests food and shelter for the winter.
4. Remove new sprouts growing at the tree base or along stems and branches. Don’t over-prune green tissues. Pruning should conserve as many living branches as possible with only a few selective cuts.
5. Spread a thin layer of composted organic mulch to blanket the soil. Cover an area at least as large as the branch spread. Mulch is nature's way of recycling valuable materials, but be careful of pests hitching a ride.
6. Aerate soils if they’re compacted and poorly drained. It’s critical not to damage tree roots living in the soil. Saturated and dense soils suffocate roots and help root diseases.
7. Conservatively fertilize with any essential element which is in short supply within the soil. Nitrogen should be used sparingly, especially under large, mature trees and around newly planted trees. Use very slow release fertilizers.
8. 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’s much easier to overwater in winter.
Trees sense changing seasons by temperature, by a dormancy timer in the leaves and buds and by the amount of light they receive. Old leaves, buds and inner bark all have pigment sensors which read the seasons. As days shorten in fall, one pigment called phytochrome sends a message across the tree to shut down for winter.
Getting ready for winter in an organized way is called senescence. Senescence in trees is an ordered shutting down of summer growth and the conservation of valuable resources. Senescence brings both fall colors and renewed spring growth.
Many materials collected or manufactured by a tree during the growing season are withdrawn from soon-to-be-shed and dead leaves. Tree waste materials are left behind. The last bit of tree food is stockpiled in the living cells of the outer annual growth rings. Twigs, branches and roots become collection sites and warehouses of materials needed for another season to come.
Within the tree, biological doors and windows are being closed and locked. From the moment last spring's green leaves expanded and began to make food, winter dormancy has been the designed end. The process of spring and summer growth reset and started a dormancy timer that hurries tree preparations for winter.
A tree-filled landscape in late fall and winter can be mistakenly thought to be asleep. Fall and winter trees are not sleeping, but are simply still -- truly counting the days until spring.
Most of the growing points in the tree are protected inside overcoats called buds. Each growing point waits for a correct message to signal a new season of growth. Only then will it be apparent whether a tree has put aside and saved enough resources to respond to the new season of growth.
Trees are investments that require a small amount of care. For the sake of your tree's quality of life and your own, take a few minutes to winterize your tree. For trees, wonderful springs come from well-tended fall and winter.
For more information about tree health care, contact a professional arborist or community forester.
(Kim D. Coder is a professor of tree biology and health care with the University of Georgia Warnell School of Forestry and Natural Resources.)