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'Topping' trees can do more harm than good

April 20, 2008

Trees provide so much to our communities, our homes and our lives. Healthy trees provide shade, reduce energy costs, prevent soil erosion, filter pollutants from the air and water, beautify our landscapes and increase property values.

Some tree owners worry that branches will fall down when trees grow large, causing property damage or harm. They believe trees must be shortened, or "topped," to make them safer.

Tree topping is the removal of large amounts of leaves and branches from a tree's crown. In some cases, all the leaves and branches are removed, leaving large stubs where branches were cut.

If you are topping a tree to make it smaller, don't. It doesn't work! After a tree is topped, it grows back rapidly in an attempt to replace its missing leaves. Leaves are needed to manufacture food for the tree. Without new leaves, the tree will die.

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Tree-topping hurts trees, shortens their lives and creates dangerous trees that will drop branches in the future. With proper care and maintenance, trees can remain safe and valuable without topping.

If you don't want a tree to get too big, then it is best to remove the large tree and replant with a tree that doesn't grow too tall. You can't stop trees from growing tall by topping. If you do succeed, you have killed them. A tree's leaves manufacture its food by photosynthesis. Repeated removal of a tree's food source literally starves the tree over time. When it is topped, it must use stored food (reserves) to grow back new leaves and branches.

And topped trees are ugly. They lose their natural, organic look. The tree's natural form and appearance, that takes years to grow, can be permanently destroyed in a few hours by an uninformed tree worker or landscaper who tops.

Also, topped trees become hazardous. According to Alex Shigo, author of books on the care of trees, topping is the most serious injury you can inflict upon your tree. Topping creates unsafe trees in three ways:

· It opens the tree up to an invasion of rotting organisms. A tree can defend itself from rot when proper cuts are made in relationship with branch collars. It cannot stop the spread of decay when it is topped. Rotted limbs - or the entire tree - might fall years after topping.

· The new quick-growing branches are weakly attached and break easily in wind or snowstorms - even many years later, when they are large and heavy.

· The thick growth of new branches caused by topping make the tree top-heavy and more likely to catch the wind, increasing the chance of storm winds blowing branches out of the tree. A tree can be properly pruned or thinned to allow wind to pass through the branches.

When you think about it, the cost of tree topping is greater than not topping. Once it is topped, a tree must be topped every few years and eventually must be removed when it dies or the owner gives up. Proper pruning actually improves the health and beauty of a tree, requires less maintenance and costs less in the long run.

Obtain free tree-care information from your local cooperative extension office or state forestry office or go to www.patrees.org.

Hire a certified arborist to care for your tree. They've received extensive training and passed a comprehensive exam on tree care practices. To learn more about arborist certification, go to www.patrees.org. or www.treesaregood.com.

Eastern tent caterpillars

The eastern tent caterpillar will soon start hatching in our area. Local residents might see nests once our trees start to develop leaves.

Tent caterpillar nests are commonly seen on wild cherry trees along country roads or in fence rows. They can also be found on apple and crabapple trees as well as hawthorn, maple, cherry, pear and plum trees.

The eastern tent caterpillar winters as egg masses on tree branches. The eggs hatch about the time the buds start to open.

Working together, the caterpillars form a silken nest in the crotch between tree branches. The tent is the home where caterpillars will stay in rainy weather and during the heat of the day. Then they go out and feed on the expanding leaves of the tree. As the caterpillars grow, they expand the nest until it is at least 12 inches long. The adult caterpillars will become two to two and a half inches long.

Generally the eastern tent caterpillars don't do much harm. They complete their life cycles quickly, and the tree will grow back the leaves. But the loss of the leaves and the need to grow new leaves can weaken the tree.

Most people are not too concerned about a wild cherry in a fence row, but if caterpillars get on your crabapple tree and other landscape trees, you might wish to control them.

When the nests are small, it's easy to remove them with your hands and destroy the caterpillars.

Various beneficial wasps also attack young caterpillars. You should not put a rag soaked in gas on the end of a stick and burn the nest. This can cause more damage to the tree than the caterpillars will. If you can't remove the nests by hand, you can use a long stick to wind the nest up to remove.

The young caterpillars can also be controlled with a spray application of an organic insecticide that has Bacillus thuringiensis var. kurstaki. This material works well on young caterpillars, but once they get an inch or more long, control will not be very effective. You can also use carbaryl (Sevin) and Malathion and spray the foliage around the nest so they will be feeding on it.

Bob Kessler specializes in consumer horticulture and energy for Penn State University. He can be reached weekdays at 717-263-9226 or by e-mail at rxk4@psu.edu.

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