Late fall and winter are the seasons for some of nature's most severe weather. Storms in all shapes and forms create havoc throughout the country. One of the greatest dangers posed by storms are presented by falling trees. Unsafe trees are a threat to lives and property.

Many shade and ornamental trees are damaged throughout the year by windstorms, lightning or ice and snow accumulations. Damage usually consists of a few broken branches. However, more severe damage - such as splitting or pulling apart of branch unions, removal of large areas of bark, twisting and splitting of the trunk, or even uprooting - pose possible dangers.

A few tree species, including Chinese elm, silver maple, box elder and various poplars, have brittle wood that is easily broken. These rapidly growing trees cause a considerable amount of damage to homes, cars, buildings and utility liens each year. Homeowners should be aware of these characteristics and avoid planting them close to potential targets. If such trees are already growing in these locations, preventive pruning, bracing, or cabling may help reduce storm damage this winter. This is particularly true as the tree grows in size and the weight and surface of the leaf and branch area increases.

Over the years, growing trees will "catch" more wind and become heavier, so they are prone to increased mechanical stresses, thus increasing the chances of failure. Larger trees will also affect an increased area should they or their larger limbs fall. This means that power lines, homes and other structures that might not have been threatened a few years ago might suddenly be under threat by a tree that has grown. Preparing trees for these natural disasters is a must and should be done well in advance of the stormy season. To help ease these dangers, have a professional arborist evaluate your trees. Doing this will help you determine potential weaknesses and dangers.

Look for the following warning signs"

• Wires in contact with tree branches. Trees may become energized when they are contacted by electric wires.
• Dead or partially attached limbs hung up in the higher branches that could fall and cause damage or injury.
• Cracked stems and branch forks that could cause catastrophic failure of a tree section.
• Hollow or decayed areas on the trunk or main limbs, or mushrooms growing from the bark that indicate a decayed and weakened system.
• Peeling bark or gaping wounds in the trunk also indicates structural weakness.
• Fallen or uprooted trees putting pressure on other trees beneath them.
• Tight, V-shaped forks which are much more prone to failure than open U-shaped ones.
• Heaving soil at the tree base is a potential indicator of an unsound root system.

Remember, too, that a tree is a living thing, and its integrity and stability change over time, so don't assume that a tree that has survived ten severe storms will necessarily survive an eleventh.

Homeowners who are looking for someone to assess their landscape can contact the National Arborist Association (NAA), a 63-year-old public and professional resource on trees and arboriculture. An easy way to find a tree care service provider in your area is to use the "Locate Your Local NAA Member Companies" program. Call 800 733-2622 or do a zip code search at the NAA's Web site: www.natlarb.com.