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ARBORICULTURE: WINTERIZING TREES
  MG Manual Reference
Ch. 13, pp. 16 - 18

It is often necessary to give a little extra attention to plants in the fall to help them over winter and start spring in peak condition. Understanding certain principle and cultural practices will help you avoid winter damage of ornamentals. Frost damage is caused by moisture condensing on the leaf and forming ice crystals by drawing water from the plant. This dehydrates the plant and is why frost damage looks like a burn.
Select hardy plants. Grow plant materials that are native or are known to be winter hardy in your area.
Remove snow with an upward motion
Remove snow with an upward motion
Select appropriate site. Plant less hardy plants on the north, northeast, or eastern side of a building or other barrier to protect from prevailing winds and intense winter sun. These exposures will also delay spring growth, thus preventing injury to new growth of flowers from late spring frost.
Avoid low spots that create frost pockets and sites that are likely to experience rapid fluctuations in temperature.
Follow recommended cultural practices. Plants that are diseased or deficient in nutrients are more susceptible to winter injury than strong, healthy plants.
Prune properly. Avoid late summer pruning, which stimulates new, tender growth and reduces the supply of nutrients available to the plant through the winter. Remove narrow branch angles which are prone to breakage in heavy snows.
Water properly. If autumn rains have been insufficient, give plants a deep soaking that will supply water to the entire root system before the ground freezes. Watering during January, February, and March, when there are warm days, is also important. A two-inch layer of mulch reduces alternate freezing and thawing of the soil, which heaves some shallow-rooted plants and can cause significant winter damage.
Protect against damage. Use the following techniques if you determine that it is necessary to protect your trees or plants from winter temperatures.
Cover plant at night to trap radiant heat. Remove cover in the morning to allow radiant heat to be absorbed.
Place an incandescent light low inside the canopy; be careful not to burn the trunk.
Windbreaks of burlap, canvas, or a similar material can reduce the force of wind and also shade the plants. Wrapping trunks with burlap can also protect against bark splitting.
A fine, gentle, continuous spray of water can provide protection as low as 20° F. When the air temperature drops below freezing, the water sprayed onto the plant begins to form ice. During the process of freezing, water gives off heat and enough heat is absorbed by the plants to prevent them from freezing. As long as water is applied continuously, the plant remains above its freezing point. Application of water must begin when the temperature at plant level reaches 34° F and must be constant throughout the period when the air temperature is below freezing and continued until all ice has melted off the plant. A stationary or rotary sprinkler will give satisfactory results. This technique can lead to limbs breaking from the weight of the ice. Wrapping trunks with burlap can prevent bark splitting.
Antitranspirant compounds: reduce the temperature at which water freezes. These compounds degrade rapidly and are of little value to home owners unless repeat applications are made throughout the winter months.
Antibiotics kill bacteria on plants which results in ice forming less readily.
If Winter Injury Occurs...

Wait until midsummer before pruning because even plants that look dead may still be alive. The extent of winter damage can best be determined after new growth starts in the spring. At that time, prune all dead twigs or branches back to within one quarter of an inch above a live bud, or to the nearest live branch.
If discoloration on narrow-leaved evergreen needles is not too severe, they may regain their green color or new foliage may be produced on the undamaged stem. Broad-leaved evergreens showing leaf damage will usually produce new leaves if branches and vegetative leaf buds have not been too severely injured. Damaged leaves may drop or be removed. Prune to remove badly damaged or broken branches to shape plant and to stimulate new growth.
An application of fertilizer to the soil around winter-damaged plants, accompanied by adequate watering, will usually induce new growth to compensate for winter injuries. However, special care should be given throughout the next year to plants injured by winter's cold. The dry months during the growing season can be particularly damaging as the plants are weak and often unable to survive the stress of drought. Be sure to water adequately.


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