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Trees are vital to life on our planet. You can't replace a large tree in your lifetime. All trees eventually die. We need to maintain and prolong the life of the ones we have. We also need to remove the ones that are a hazard.
So how can we help prolong a trees life? For better health (less stress) the two practices that will help the most are water and mulch.
Proper pruning is also critical. Never take off more than one-third of the tree's crown at one time. Corrective pruning when the tree is young gives you the structure that will help the tree withstand wind.
Remove dead wood on large trees so fungal diseases can't get started. If you think your tree is a hazard, get the opinion of a professional. They can go through a check sheet with you.
There is one practice we would like to see die out completely -- that is topping. Topping signals the beginning of the end of the tree. From the Tree City USA Bulletin #8 by the National Arbor Day Foundation, eight good reasons why not to top are:
Good pruning practices rarely remove more than 1/4 to 1/3 of the crown, which, in turn, does not seriously interfere with the ability of a tree's leafy crown to manufacture food. Topping removes so much of the crown that it upsets an older tree's well-developed crown-to-root ratio and temporarily cuts off its food-making ability.
A tree's crown is like an umbrella that shields much of the tree from the direct rays of the sun. By suddenly removing this protection, the remaining bark tissue is so exposed that scalding may result. There may also be a dramatic effect on neighboring trees and shrubs. If these thrive in shade and the shade is removed, poor health or death may result.
The large stubs of a topped tree have a difficult time forming callus. The terminal location of these cuts, as well as their large diameter, prevent the tree's chemically based natural defense system from doing its job. The stubs are highly vulnerable to insect invasion and the spores of decay fungi.
At best, the wood of a new limb that sprouts after a larger limb is truncated is more weakly attached than a limb that develops more normally. If rot exists or develops at the severed end of the limb, the weight of the sprout makes a bad situation even worse.
The goal of topping is usually to control the height and spread of a tree. Actually, it has just the opposite effect. The resulting sprouts (often called water sprouts) are far more numerous than normal new growth and they elongate so rapidly that the tree returns to its original height in a very short time -- and with a far more dense and dangerous crown.
Some species of trees are less tolerant to topping than others. Beeches, for example, do not sprout readily after severe pruning and the reduced foliage most surely will lead to death of the tree.
A topped tree is a disfigured tree. Even with its regrowth it never regains the grace and character of its species. The landscape and the community are robbed of a valuable asset.
To a worker with a saw, topping a tree is much easier than applying the skill and judgment needed for good pruning. Therefore, topping may cost less in the short run. However, the true costs of topping are hidden. These include: reduced property value, the expense of removed and replacement if the tree dies, the loss of other trees and shrubs if they succumb to changed light conditions, the risk of liability from weakened branches, and increased future maintenance.
When you are out looking at trees and their hazard, the key question is the potential target that may exist. A picnic table under a tree makes the people sitting there a target. A road or walkway where a tree may fall is a potential target. If there is no target, the tree is not considered a liability. Determining risk assessment on a tree depends on the target, but also how many things are wrong with a tree. The following are hazards you want to check for:
Are there large dead branches in the tree?
Are there detached branches hanging in the tree?
Does the tree have cavities or rotten wood along the trunk or in major branches?
Are mushrooms present at the base of the tree?
Are there cracks or splits in the trunk or where branches are attached?
Have any branches fallen from the tree?
Have adjacent trees fallen over or died?
Has the trunk developed a strong lean?
Do many of the major branches arise from one point on the trunk?
Have the roots been broken off, injured or damaged by lowering the soil level, installing pavement, repairing sidewalks or digging trenches?
Has the site recently been changed by construction, raising the soil level or installing lawns?
Have the leaves prematurely developed an unusual color or size?
Have trees in adjacent wooded areas been removed?
Has the tree been topped or otherwise heavily pruned?
Trees that are nine inches in radius must have a tree inch (1/3) outer shell to be strong enough to withstand normal winds. If over 1/3 of the trunk is damaged all the way to the outside, then a 2/3 (six inches) thick shell must be intact.
If you are interested in more information on hazardous trees, you can purchase a copy of "Risk Assessment Guidelines for Hazard Trees" by sending a check (payable to Brown County Treasurer) for $1.50 (includes postage and handling) to: Tree Hazard Info., UW-Extension, 1150 Bellevue ST, Green Bay, WI 54302.
Defects in trees present future hazards and a shorter life for the tree. It is critical to get our trees started off right so there are the least amount of defects in the future. The following are some guidelines:
Plant the tree properly.
Prune and train the tree for strong, well angled branching. Narrow crotches cause included bark and a weak branch (silver maple and green ash are the worst).
Mulch trees with 3- to 4-inches of a loose woodchip mulch tapered to 1" at the trunk.
Supply one inch of water per week.
Prune off no more than 1/4 to 1/3 of the crown of the tree in any year. The tree will not cover over wounds (no energy) and rot will be introduced, if you prune off too much of the crown.
If a tree has more than 50% dieback (defensive dieback) on the top, it won't recover. Removal is best before the tree becomes a hazard.
Splits are caused by pruning wounds or dead roots.
If you are cutting off limbs, don't cut one limb above another or a group of limbs in one place all at one time. That type of wounding weakens the tree enough to make it a potential hazard.
Prune out dead branches so calluses can form over wounds so decay does not enter the trunk wood.
Don't destroy tree roots during construction. Keep machinery and root cutting away from trees 1.5 times the inch diameter of the tree in feet (example: on a 10-inch tree keep a 15-foot radius from the trunk). Further is better if you can.
Cabling and brancing a tree helps to keep the limbs moving in unity and so gives them less stress. It does not eliminate them as a hazard. Cables should be placed 2/3 the way up and the tree bracing just below the crotch.
--Published in Northeast Wisconsin Horticulture Newsletter, October 1998.
