Garden Help: Preparing our tree canopy for summer storms

Florida Times-Union (Jacksonville, FL)

With COVID-19 dominating the headlines, we may not be aware of the approach of summer right around the corner. With the advent of summer comes thunderstorms and hurricanes. Perhaps it is time to be thinking about the trees around our homes.

There is no "risk-free" tree. However, there are strategies that we can undertake that can create a more wind-resistant tree canopy -- plant more wind-tolerant trees, prune properly and conduct routine tree inspections.

WIND-TOLERANT TREES

Research by the University of Florida performed in communities that received hurricane force winds from 1992-2005 identified several trees that appeared to be somewhat resistant to wind damage. It is thought that the growth form of the trees helped them resist wind better.

The trees that appear to do better are: live oak, southern magnolia, sweetgum, holly, sycamore, swamp chestnut oak, bald cypress, sabal palm and blackgum.

There were also several trees that were identified as trees with poor wind resistance. Those trees include pecan, tulip poplar, laurel cherry, Bradford pear, laurel oak, queen palm and lacebark elm.

Creating a wind-resistant tree canopy includes planting more of the wind-tolerant trees and removal of the wind-intolerant trees if they are likely to cause property damage.

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Planting a wind-tolerant tree is only half the equation. A tree needs to have ample space for its roots to grow. Trees with more rooting space survive better. This is one of the most important lessons learned from prior storms. Trees that are planted in large yards and parks with plenty of rooting space outperform by a large margin the trees that were planted in too small of a planting space. The current recommendation is that small trees need a rooting space of at least 10 by 10 feet; medium trees need 20 by 20 feet; and large trees need at least 30 by 30 feet. This also takes into account that trees need good soil structure to send roots deeper. A healthy soil allows roots to grow down 18-24 inches. Trees growing in compacted soil, or soils with high water tables, have shallower roots, and are not as wind-tolerant.

PROPER PRUNING

Branch failure is the easiest type of failure to prevent. This is done through proper pruning beginning when the tree is young. When you are out in the landscape, look up. Take note of any large dead branches. Major deadwood over any structure is an immediate concern and should be removed. The type of branch attachment is also important. Take a look at how the major branches are attached to the trunk. If the attachment of the branch looks like a "V" rather than a "U", it is a weaker branch attachment. The reason V-shaped branch attachments are a problem is because bark gets embedded in the joint as the branches grow together and weakens the attachment. This condition can be even more of a risk when the tree has more than one trunk. Multi-trunked trees are especially prone to splitting apart because of poor branch attachment.

How trees are pruned is important. A recent study by the University of Florida showed that properly pruned trees had considerably less damage than unpruned and improperly pruned trees. Thinning out the canopy by overlifting the crown through the removal of large lower limbs and removing interior branches (lions-tailing) is not proper pruning.

It is a myth that trees that are thinned out are more storm resistant. In fact the opposite is true. An overly thinned out tree (lions-tailed) has a large amount of weight at the end of the branch, making it more likely to break. In addition, trees that are overthinned are harder to restore when repairing storm damage. Research performed by the University of Florida has taught us that pruning trees by using reduction cuts and structural pruning results in trees that resist wind and therefore receive less damage.

TREE INSPECTION

A periodic inspection of the branches, trunk and root area can reveal problems with a tree before they become major. Trunk and root defects are harder to detect than branch defects. The most obvious type of trunk defect is a cavity. Large cavities with decay should be inspected. Any vertical crack in the trunk of the tree that goes deep into the wood of the tree is a warning sign of structural problems and any horizontal crack is a sign of imminent trunk failure. Any mushroom or mushroom-like fruiting structure coming out of the trunk of the tree is a sign that the tree has internal decay and should be inspected more thoroughly by a tree professional.

There is no way of knowing how much of the tree structure has been lost to decay without some further testing. The arborist inspecting the tree may recommend pruning or cabling to relieve stress on the trunk, however; if the defect in the trunk is serious, removal of the tree may be the only means to solve the problem.

The part of the root system that bears most of the load in holding the tree up is the root plate. If you picture the tree as a wine glass, the root plate is the base of the wine glass. Many trees have had their roots covered by soil during construction activities. Mulch volcanoes are formed when mulch is piled over the root flare and against the trunk of the tree. Both situations are bad for the tree because the bury the roots and promote disease. It also makes inspection of the root flare difficult. If the root flare of a tree has been covered by soil or mulch, it is important to uncover it for a proper inspection.

Look for any cavities at the base of the tree, or mushrooms originating from the base or roots of the tree as a sign of possible root decay. Avoid cutting roots closer than five times the trunk diameter. Any damage to the root plate by construction, or other means, is a cause for alarm. Recall the wine glass analogy and imagine how unstable the wine glass would be if part of the base were gone. When tree roots are cut or damaged by construction, the anchoring function of the roots is compromised. A Certified Arborist should be called in to inspect the tree if any problems with the root system are suspected.

Finally, just a word about hiring an arborist. There is no licensing for arborists in Florida. The best thing we have is a program by the International Society of Arboriculture (ISA) that has a credential called a "Certified" arborist. Being certified requires professional experience and knowledge of the best techniques in the industry. Certified Arborists must attend training courses and continuing education classes to learn the latest tree care research.

It is also a good idea to verify that the folks working on your tree have liability and workers' compensation insurance. Sometimes it is worth it to call their insurance provider to verify that a policy is current. Avoid arborists that demand payment in advance, do not offer a written estimate or incorporate high-pressure sales tactics. To search for an ISA Certified Arborist in your area go to www.treesaregood.org/findanarborist.

There is no way to completely eliminate the risk of a tree falling and causing damage in a storm. With regular inspection of their landscape, homeowners can significantly reduce the risk by identifying defects in their trees and taking care of them before they become a problem. More information on trees and storms can be found on the University of Florida Environmental Horticulture Website at hort.ifas.ufl.edu/woody/stormy.shtml.

Larry Figart is urban forestry extension agent from the University of Florida/IFAS.

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