July 7, 2008

It’s Hurricane Season – Are your trees in shape?

By Pam Brown, Urban Horticulture Agent, University of Florida/IFAS Pinellas County Extension

As hurricane season arrives, there are many tree companies that are out and about offering to prune large trees and palms. Much of the pruning that is done can actually create a situation that puts the tree in more danger of failing in high winds than of providing protection. There has been a lot of research done at the University of Florida on the proper way to prune trees and the way that trees behave in high winds.

First, allow me to provide a bit of biology 101 refresher. The green leaves on trees and the green fronds on palms are the source of the food, through the process of photosynthesis, that these plants need to thrive and grow. When you remove green leaves and fronds, you reduce the ability of the plant to produce the food necessary to support the roots and top growth adequately. Fertilizer contains nutrients that are necessary for making proteins and enzymes but it is not the source of the food necessary to sustain the tree.

Let’s look at palms since they are so often badly pruned. When green fronds are removed, the palm is weakened. And, when all but a few of the fronds are removed in what is commonly called hurricane pruning, the trees is in more danger of failing in the wind. Those lower, fronds are mature, hardened fronds that protect the newer, more fragile fronds near the growing point of the palm. Without the mature fronds for protection, the top of the palm is more likely to sustain wind damage during hurricanes or other high winds. In addition, when this type of pruning is continued over time, the palm is weakened and may develop nutrient deficiencies and eventually decline and die. Palms are pruned primarily for people reasons and not the health of the palm. It is perfectly acceptable to remove dead fronds and blooms or fruit. And, I find that when a frond is hanging too low over the sidewalk, just cutting off the tip end of the frond will make it light enough to spring up out of the way of pedestrians. Removing the frond bases that remain attached to the trunk with a chainsaw creates wounds where insects or disease can possibly enter.

Our large shade trees are also being damaged by improper pruning. According to Dr. Ed Gilman of the University of Florida, this common malpractice on large trees of removing many or all interior low branches is considered over-thinning or “lions-tailing”. He states that “When people prune trees in this abusive manner, excessive live tissue is removed from the tree and no structural pruning is performed. This creates poor form and numerous wounds, and the tree becomes more prone to failure especially if there are few trees nearby. Old trees can decline as a result of removing too much live tissue. Only a small amount of live tissue may be too much to remove on a mature or over-mature tree. There should be a very good reason, such as to reduce likelihood of branch failure, when removing more than ten percent of the live foliage on mature trees.” Also, please do not allow anyone to top your trees for any reason.

Reducing the amount of foliage on the ends of the branches, and thus the weight, is a better way to reduce risk of branch failure during high winds. The canopy can be opened up without removing all of the interior branches and attached foliage. An arborist certified by the International Society for Arboriculture is trained in the proper way to prune and protect trees. However, all certified arborists are not equal. When requesting a quote from an arborist, ask to see their certification card, proof of liability insurance (ask for this no matter who you hire), references, and also ask if they will be with their crew when the work is done. I would suggest three quotes and then maybe even go to look at some trees that they have pruned.
You can find certified arborists in our area on the Internet at: Or, you may call our Lawn & Garden help line (582-2110) Tuesday – Thursday and request a copy of the current list.

The following links lead to the extensive University of Florida information on tree pruning on the Internet:

In addition, you can view a 50 minute video called “Trees and Storms” on the Internet at: Go to the right side of the page under "Hot Topics" and click on “Trees and Storms”.

Trees add considerably to the value of our property and keeping them healthy while providing protection from damage to our homes is a delicate balance that requires planning and caution. I hope that you will do your homework before allowing just anyone with a truck access to your trees.

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