February 2017
The Magic of Gardening

Pruning Trees for Safety

 

A tree that has just been topped.

Homeowners often start to worry about large trees near their home during the spring tornado season. In some cases, the fear is warranted, but the solution I often see employed is harmful to trees and may actually make the tree more dangerous in the long run. I am talking about tree topping, a ubiquitous practice across all Alabama. Tree topping is the practice of cutting large limbs back to stubs. Often a topped tree will have the majority of its canopy removed at one pruning event that can lead to several problems for the tree.

The ends of these stubs will do two undesirable things. First, they will develop numerous aggressive sprouts that may grow several feet in one season. These new water sprouts are poorly attached and very top heavy. They can get quite large in only two or three years. Second, the large stubbed limb will often start to decay because the wound is unable to seal up. When these two problems are combined it is a recipe for disaster after a few years of regrowth and rotting. These weakly attached, top-heavy limbs can easily break off and the rotting major limb exacerbates the problem. In addition, the excessive pruning from topping weakens trees by removing stored food reserves and reducing the trees’ abilities to make new food reserves. Once trees are severely weakened, they are subject to greater attack by both insects and disease.

You are likely wondering by now if there is a safe way to reduce the risk of a tree falling on your home? The answer is yes and no. I know this sounds like an answer from Hank Kimball, the county agent on the "Green Acres" sitcom (check him out for a laugh at http://tinyurl.com/hankkimball).

The way I like to explain how to make a large tree safer is to think of the canopy as a gigantic wind sail on a large boat. If you are out on the water and a storm is approaching, you may completely lower the sails to eliminate the chance of capsizing the boat. Removing all the foliage (such as is done in topping), however, is not practical or a good practice. Another option on a sail boat is reefing the sail. This practice reduces the area of a sail so wind resistance is lessened. In pruning, we can accomplish this by thinning the tree canopy with many small cuts, mostly on the outer edges of the canopy where the leverage is greatest for toppling a tree. We can also open up the canopy to allow wind to move through the tree rather than being trapped.

Previously topped pecan trees with large water-sprout growth after one year.

 

A trained arborist will know how to implement this practice to make your tree safer if it is possible to do so. If it is not practical or possible to make the tree safer, a qualified arborist may recommend tree removal, which is much preferred to topping. Because trees are long lived and require a significant amount of time to grow and become mature enough to provide benefits of shade, wind resistance, sound reduction and beauty, it is important to hire only well-informed professionals to work on them. For a tree, once damaged is always damaged. Unskilled work often results in damage or structural weakness the tree will keep throughout its existence. The skill level of the person hired will dictate the safety and longevity of your tree.

If at all possible, try to hire an International Society of Arboriculture Certified Arborist. This is more than just a credential. Obtaining a Certified Arborists’ license requires the applicant to pass an extensive examination about trees and tree care. Someone with this certification is more likely to be knowledgeable about tree biology, tree care and the best pruning methods to use. You can find a local certified arborist at www.treesaregood.com.

 

Tony A. Glover is a County Extension Coordinator in Cullman County.