Tree pruning is both an art and a science. Pruning is done for several reasons: in order to achieve a certain effect or look in landscape (the artistic side), or for health or growth reasons (the scientific side). When done properly, pruning can improve the appearance of a tree and increase its life expectancy. Proper pruning opens the canopy of the tree to permit more air movement and sunlight penetration, for example.

However, the reverse is also true. When done improperly, pruning can drastically cut short a tree’s life expectancy, even killing it in some extreme circumstances.

To avoid such situations, tree care professionals adhere to accepted standard of practices when pruning trees, called the American National Standard for tree pruning. This standard, designated ANSI A300, was implemented in 1995 and must be followed for pruning trees in all situations and locations.

Several indicators will tell you whether or not your tree is sick and in need of attention. Warning signs of structural instability include cracks in the trunk or major limbs, hollow and/or decayed areas or the presence of extensive dead wood. Mushrooms growing from the base of the tree or under its canopy could also indicate root decay.

It pays to be highly suspicious of any tree that has had construction activities such as trenching, addition or removal of soil, digging or heavy equipment movement anywhere under the spread of its branches. These activities can cause root death, which in turn could lead to the structural instability of the tree.

Even a healthy and otherwise safe tree can become hazardous if it is growing close to electric power lines. Someone who touches or climbs a tree while it's resting on a live power line could be electrocuted. Any tree that has limbs within 10 feet of overhead lines should be considered hazardous, and should be left to the professionals.

If you suspect a hazardous condition, it will pay to have your tree evaluated by a professional – you could be held responsible for any damage or personal injury caused by a tree on your property.

Most often, trees change color with the seasons. Changing weather conditions will affect the balance of the chemical composition in a tree’s leaves, thus changing the color of the leaves.

Color-changing leaves make for a beautiful display in the fall, but early changes in leaf-color can be a sign that your tree is stressed and susceptible to insect and disease attack.

Occasionally only one or two limbs of the tree will show premature color changes, and this could in fact be a sign of a disease at work, weakening only the infected limbs. But it’s far more common for the entire tree to show color change, which is usually linked to root-related stress. Trees will respond to that stress by limiting their above-ground growth, evidenced by their premature color change.

If the leaves on your trees are changing color before the fall season, consult with a professional arborist, who can identify any problems and offer solutions.

Winter weather can be even more harmful to trees and shrubs that are already stressed, so in order to make sure they survive the cold, start by making sure they’re in good health year-round.

Proper location for plants is step one to making sure they’ll survive, no matter the weather conditions. Certain areas around a home’s landscape offer different climatic conditions. These areas, known as microclimates, should be understood and used for planting appropriate trees. A professional nursery operator or arborist can help you choose the best tree and the ideal location to plant that tree around your house.

In winter, the ground around the root system of the plant or tree freezes, stopping or slowing the circulation of water in the tree. If the root system is frozen, the plant is not able to draw in water. Placing mulch around a tree produces a year-round benefit because it not only increases the microbial activity and fertility of the soil underneath it, but it also acts as insulation between the root system and the outside climate. This helps retain moisture in the root system and reduce the change in soil temperature.

Trees can also suffer from a kind of sunburn during the winter. When the sun shines brightly on a cold winter day, it may heat up the bark of a tree to a temperature that stimulates cellular activity. But as soon as the sun's rays are blocked, the bark temperature drops quickly, rupturing and killing the active cells, causing “sunscald,” the symptoms of which are elongated, sunken, dried or cracked areas of dead bark, generally on the south side of the tree. To prevent this, wrap the trunk of your trees with a commercial tree wrap, plastic tree guard or light-colored material that reflects the sun and reduces the temperature changes in the bark.

The weight of snow and ice on a tree can cause branches and even the entire tree to topple. Ensuring that your trees are properly pruned can make them better able to withstand the extra weight of ice and snow.

Salt used for deicing streets and sidewalks is also dangerous to trees, shrubs and grass in the winter. You can avoid injury by using only non-injurious types of deicing salts or avoiding salt applications to sensitive soil areas.

Preparing trees for natural disasters is a must and should be done well in advance. The older the tree, the heavier it becomes, increasing the chances of a fall. 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.

To help limit the chances of dangerous falls caused by storms, have a professional arborist evaluate your trees to determine potential weaknesses and dangers. You should also ask the arborist to look for signs of potential hazards, such as stress cracks, weak branches and other subtle or hidden indicators of potential hazards.

Other warning signs for you to watch out for include:

• Power lines in contact with tree branches – Trees may pick up an electric current when in contact with 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, which 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 stem.
• Peeling bark or gaping wounds in the trunk, also indicates structural weakness.
• Fallen or uprooted trees that are 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, which is an indicator of a potentially unsound root system.

Remember that a tree is a living thing, and its integrity and stability changes over time. Don't assume that a tree that has survived 10 severe storms will necessarily survive 11.

Proper treatment of any condition, insects included, begins with a proper diagnosis. A professional arborist, nursery operator or state/county extension agent can help you determine what kind of insect is in your tree.

Once the bugs are identified, it can be determined if they’re harmful to the tree, beneficial to the tree or have no effect at all.

Some insects are beneficial, because they control populations of harmful insects through predation or parasitism. It is in your best interest to keep them, so you want to avoid any treatments that take out the good bugs with the bad bugs.

But if the insect is harmful, you must ask how harmful is it if it’s worth treating. Most professional arborists operate on the philosophy of treating only when the environmental/economic risk from the insect has reached a certain threshold.

For the most part, the bugs you see in your tree are likely benign. Termites, for example, do pose a threat to trees and should be treated by a professional. On the other hand, carpenter ants don’t harm trees, but actually indicate decayed wood is present, providing a warning to you of a potentially hazardous situation.

The time of year to take care of your trees really depends on what you need to have done.

Many tree care activities can actually be carried out all year long, but spring and summer allow for the best opportunities to identify tree health problems, since a cursory inspection can tell whether the tree looks healthy compared to previous years or nearby trees of the same species.

However, most pest management activities have a very specific and narrow window of treatment that coincides with when the pest is active on the plant and/or vulnerable to the treatment.

Some experts say that in temperate climates, fall and winter are the best times to prune your trees. But pruning generally can be done anytime of year, with a few exceptions – pruning an American elm when the beetle that carries Dutch elm disease is busy flying from infected to healthy host trees greatly increases the elm's chances of infection, for instance.

The practice known as “topping,” or the cutting off large parts of a tree, is the tree care equivalent to amputation. Trees are often topped to height or shape, leaving branch stubs and little or no foliage. This causes damage to trees that includes:
Leaving large exposed wounds that the tree can't readily close.

• Ruining tree structure.
• Removing too much foliage and disrupts the tree's energy storage for future growth.
• Stimulating vigorous new growth, which is weakly attached and prone to breakage.
• Increasing tree maintenance costs.
• Destroying the tree's appearance and value.

“Lion-tailing” is another practice that severely damages trees. In this case, the inner foliage, branches and limbs of a tree are stripped bare, and the limbs left on the tree are long and bare except for a characteristic "tuft" of foliage at the end, giving the appearance of a lion's tail. This causes damage to trees that includes:

• Weakening of limbs, which may break.
• Stimulating vigorous new growth on the inner portion of the tree that is weakly attached and prone to break.
• Removing too much foliage disrupting the trees energy reserve for future growth.
• Destroying the tree's appearance and value.

Topping should not be confused with proper crown reduction pruning, which will safely reduce a tree's size and redirect its growth, nor should lion-tailing be confused with proper thinning, which is the selective removal of branches to decrease weight and wind resistance. Generally, proper pruning of either type will never remove more than 25% of the tree's foliage.

While trees add significantly to value and beauty of a neighborhood, they are also responsible for costly property damage as well as dangerous power outages. Tree failure is by far the leading cause of outages nationwide.

Trees that grow into electrical conductors present a potential hazard to an entire community if it becomes energized or wipes out a power line. This is why utility line clearance contractors trim trees in neighborhoods across the country.
However, some residents do feel that these trees are needlessly damaged. While it is critical for utilities to trim trees, sometimes severely, it is nevertheless important for them to follow tree care standards of practice.

When evaluating the quality of line clearance tree trimming, it's important to consider that the utility's primary objective is to prevent outages as well as electrical hazards. Minimally, the tree should be left in a healthy state, with at least some aesthetic value. If this cannot be accomplished, the utility may opt to remove the tree rather than create an eyesore and future problem.

Scientific research has proven that it is better from the standpoint of tree health if the trimming crew removes whole limbs with a relatively small number of large cuts versus making numerous small cuts and leaving stubbed off branches. Finally, utilities have found that removal of entire limbs helps to train the future growth of the tree away from the wires, keeping maintenance costs to a minimum while helping to insure that the tree won't need the same drastic pruning in the future.