Winter conditions severely affect trees that are already stressed, so one key to preventing winter damage is keeping your trees in good health year-round.
Protection from the elements
In winter, the ground root system of a plant or tree will freeze, stopping or slowing water circulation. Evergreens are at a greater risk than other trees, because they hold their needles in the winter -- the needles lose moisture to the atmosphere as well as to the plant itself. Because trees are not able to replenish lost moisture, leaves can dry out and fall off. To minimize the effects of winter drying, high-value evergreens can be treated with wax-like anti-desiccant substances that hold moisture in the leaves.
Snow and ice can become very heavy and break branches or even topple an entire tree. Pruning your tree can make it better able to withstand the extra weight of ice and snow. Mulch, too, produces a year-round benefit because it increases microbial activity and fertility of the soil underneath the tree. Mulch has the added benefit of acting as insulation between the root system and the above-ground temperature, which helps retain moisture in the root system and limits the fluctuation of soil temperature. Ensure that the ground is not frozen and has enough moisture before you add the mulch, and make sure that no more than 2 to 4 inches of an organic matter, such as wood chips, is used.
How road salt can be harmful
Salt used for de-icing streets and sidewalks is harmful to trees, shrubs, and grass. You can avoid damage by using only noninjurious types of de-icing salts or avoiding salt applications to sensitive areas. Some specialists feel that you can reduce salt damage by flushing the soil in treated areas with large amounts of water in the spring.
The severe ice storm of 1998 resulted in damage to many trees in eastern Canada and the northeastern United States. Ice storms are common in the region, so most trees are remarkably resilient. Trees that did not suffered major structural damage, such as split trunks, will recover over time. Trees are dormant in the winter, and damage at this time of year is less serious than if it occurs during the growing season. If a tree is reasonably healthy and only a moderate number of branches are damaged or removed, the tree should recover and in a few years will appear normal.
Page 1 of 2 -- How to encourage your trees to bounce back from winter, plus important safety tips to keep in mind when tending to your trees this season on page 2
The resilience and flexibilty of young trees
It is worthwhile to care for injured trees during the dormant season and wait until the growing season to see if they recover. Many young trees can bend over to ground level because of the weight of the ice collected on their crowns. Trees at this stage of development are quite flexible, and most will recover and regain an upright position when the ice melts.
It is best to wait for above-freezing temperatures to remove ice from trees. Attempting to do so while ice is still firmly attached will lead to bark damage and removal of the buds that will produce new growth in the spring.
Coniferous trees like spruces and firs generally suffer much less storm damage than deciduous species. Most coniferous species have narrow crowns and short, upright branches that minimize ice and snow loading. Damage to deciduous tree species is often much more severe. Trees with soft or brittle wood, like Manitoba maple, silver maple, native and European birches, and Siberian elm, are particularly affected. Oaks and ginkgo trees, species with strong wood and well-attached branches, suffer less structural damage.
Important tips to remember:
• Safety first. The many large, broken, and ice-covered branches hanging from storm-damaged trees are extremely dangerous.
• Do not go near any injured tree close to power lines.
• Pruning large branches and stems is difficult and hazardous and should be carried out only by trained and experienced arborists.
Excerpted from The Tree Doctor by Dan and Erin Prendergast (Key Porter, 2003).
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