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With the peak months of hurricane season upon us, it is advisable for homeowners to be sure their trees are properly pruned to minimize both tree and property damage due to falling limbs or total tree failure. However, there is a considerable amount of misinformation out there, creating confusion for homeowners. Letters from insurance companies or knocks on the door from roving tree service companies often create doubt and fear, causing tree owners to make hasty or uneducated decisions resulting in improper or unneeded pruning of trees.
Trees can be properly prepared for hurricane season through species selection and proper pruning. Pruning trees properly must begin when trees are young to avoid more serious problems later. The following are some guidelines to follow during the life of your tree.
Species selection is important. Some species are naturally more wind-resistant due to stronger wood and limb structure. After the hurricanes of 2004 and 2005, arborists and researches studied which species fared well or poorly after these storms. Trees which are more wind-resistant include live oak, sand live oak (a smaller and shorter cousin), sabal or cabbage palm, and southern magnolia. Fortunately, these species are all native and common to our area. Trees less resistant to wind include laurel oak, water oak, turkey oak, red maple, sweetgum, red cedar, cherry laurel (or laurel cherry), sand pine, and longleaf pine. As with the resistant species, these too are common to our area.
Tree quality is important. When buying a tree, be sure that it is a Florida Fancy (the best grade) or a Florida No. 1. A good nursery will have their trees graded so consumers know what quality they are purchasing. Poorer grades, such as No. 2, have defects which may be difficult to correct after purchase, such as limited root systems or poor branch structure.
Young trees must be properly pruned as they grow. Limbs should be spaced approximately 18 to 36 inches apart and should be attached to the trunk at no less than a 45 degree angle. Two equally sized stems growing parallel to one another are known as co-dominant leaders and are weakly attached to each other, creating a high probability of breakage during wind events. Select the better leader and prune back the other one over a one- to three-year period.
Also important is leaving lower limbs on the tree for several years after planting. These lower limbs create taper in the trunk of the tree, allowing the tree to better withstand winds.
When pruning trees, whether young or mature, never prune more than 25 percent of the foliage in any one year.
Such pruning of young trees is known as structural pruning. This pruning should occur over a period of perhaps three to five years. It creates a tree with strongly attached branches, proper taper, and a greater ability to bend naturally with the wind.
Many homeowners receive postcards or flyers from tree service companies offering to “hurricane proof” their trees. But what does this mean?
Simply removing portions of the tree hanging over the house or thinning the tree’s canopy may not be necessary or done properly. Proper pruning should involve the removal of dead or diseased branches or branches poorly attached to the trunk, as mentioned above. Co-dominant leaders, if still present, should be removed or reduced.
Avoid the removal of large limbs unless absolutely necessary. Pruning cuts from large limbs require more time to seal over and allow more time for insect and/or disease infestation.
Also important is the protection of tree roots. Tree roots cut during construction activities, such as driveways, sidewalks, irrigation lines, home additions or building, are compromised and may no longer provide proper anchoring during wind events. Additionally, a diminished root system may cause decline of the trees’ health due to inability to provide proper water and nutrients to the tree.
Lastly, the type of pruning is important. The canopy can be thinned somewhat to allow air flow during storms, but do not overprune the tree. As trees grow, they adapt to wind stresses at their particular location. Removing entire limbs or over-thinning the canopy results in a re-distribution of these wind stresses and may place too much stress on one or more limbs resulting in a limb or whole tree failure.
A good example of overpruning is a practice called “lion’s tailing,” where foliage remains at the outer end of the limb but all intermediate foliage is removed. This practice results in greater wind force at the ends of limbs and often results in failing limbs which would not have occurred otherwise. It also exposes previously shaded limbs to sunlight, creating numerous sprouts which are weakly attached and may eventually break when they get larger.
There is a great deal more to pruning trees than what I have covered here. However, the items mentioned above cover the greatest sins and should assist you when hiring an arborist or when doing the work yourself. If you do hire a tree service, be sure to ask if the work will be done or overseen by a certified arborist. For more information, contact your County Extension Service, your county forester or a certified arborist.
Eric H. Hoyer is a certified arborist, a certified forester, a registered consulting arborist and a qualified tree risk assessor with Natural Resource Planning Services Inc. He can be contacted at firstname.lastname@example.org.