I feel as though I’ve been raking nonstop for the past month. Why do deciduous trees have the need to keep me so busy each autumn?
A few weeks ago, as the days began to get shorter, humans and animals were not the only ones to take notice. Plants are sensitive to day length, too. In this case, deciduous trees and shrubs started preparing for winter as the dark period of each day grew longer. The plants started building up a layer of corky cells at the base of the leaf petiole, where the leaf attaches to the branch. The flow of fluids in and out of the leaves gradually slowed as a result of these new cells. This layer of cells, called an abscission zone, sealed the branch against water loss and disease penetration and allowed to leaf to fall away.
Trunks, branches and stems have a protective layer of bark to shield them from the cold temperatures and drying winds of winter weather. Evergreens have a waxy coating on their narrow needles or scales, which helps prevent moisture loss and protect them against the elements. Tender leaf tissue of deciduous trees and shrubs do not have the protection necessary to overwinter in our climate. So the tree discards them.
While the above ground parts of trees and shrubs are resting, the roots can continue to grow below ground during the winter. Whenever the soil is warmed — say on one of those wonderful 50 degree days in January — the roots in the warm portion of the soil will grow a bit. And if no measurable precipitation has fallen in the previous few weeks, such a day would be a good time to pull out the hose and do a bit of winter watering.
If you haven’t done so already, wrap the trunks of young trees to protect tender bark. Young trees that haven’t built up a layer of corky bark are susceptible to damage when the strong winter sunlight warms the trunk during the daytime. The warmth encourages activity in the conductive tissues. As night falls and temperatures plunge, the active tissue is killed.
Another winterizing activity for woody plants is to protect them from small rodents that seek shelter in mulch or fallen leaves around the base of the plant. Leaf litter should be raked up to eliminate a habitat for critters. While mulch benefits trees, if piled against the trunk of the tree it can promote insect and disease problems as well as host mice and other small animals.
Trees are a big investment, but they pay wonderful dividends when they receive the care they need.
Colorado State University Extension in the City and County of Broomfield provides unbiased, research-based information about 4-H youth development, family and consumer issues, gardening, horticulture and natural resources. As part of a nationwide system, Extension brings the research and resources of the university to the community. The Broomfield County Extension office is at 1 DesCombes Drive, Broomfield, 80020. For information, call 720-887-2286.
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