Assessing Hurricane-Damaged Trees and Deciding What to Do

Setting Priorities Immediately After the Storm

After a storm, evaluating trees for damage should occur as soon as possible. Ranking trees into priority groups, those that require immediate attention as well as those that can be treated later is an important step to recovery. What follows are recommendations for setting priorities and guidelines for decision making.

The most important priority is to determine if the tree poses an unacceptable safety risk (e.g., high risk, hazard) to humans or animals or is endangering property. Trees become a potential risk when a target—a structure, vehicle or person—could be struck by a falling tree or any of its parts. Therefore, a tree can be considered an unacceptable risk if any part that falls would result in damage to property, people, or other valuable trees.

Immediate Attention

The situation depicted in these photos pose a direct threat and should be taken care of immediately. The trees shown in Figures 1 and 2 need to be removed, while the tree in Figure 3 needs to be pruned as soon as possible.

In these situations, the work should be performed by a certified arborist or properly trained professional.

Trees That Do Not Require Immediate Attention

Keep in mind that many trees can be saved with appropriate treatment. There is no need to rush out and remove trees that do not pose an immediate safety hazard. Trees can recover from substantial damage, and what looks awful at first may be judged as less serious by an experienced professional.

Who Should Clean Up After the Storm?

Now that we have discussed setting up priorities, it is important to get the right tree care professional for the job. Homeowners should not attempt to do all the work themselves.

Certain situations require advanced training and are best handled by arborists certified by the International Society of Arboriculture (ISA). These include removing a leaning tree or broken limb near a house or other target, restoring a damaged tree that could be saved, evaluating tree risk potential, and reaching limbs that require climbing and pruning. Likewise, only qualified line-clearance arborists should work near electrical utilities. Call the electrical company to report tree limbs that have fallen on or are hanging over a power line.

Keep in mind that storm damage cleanup is extremely dangerous, even for professionals. Numerous injuries and deaths occur during cleanup after storms. When working with trees in the aftermath of a hurricane, it is essential to look up, down, and around. Beware of dangerous broken limbs that are hanging or caught in other branches overhead and may fall. Safety should be a priority. If in doubt, stay safe and find the right person to do the job.

Not All Trees Need to Be Cut Down!

A common reaction after a windstorm is to remove all trees to avoid future problems, especially if a tree has fallen on a home or other valued property. However, not every tree poses a high risk. Unfortunately, few communities and decision-makers realize that the benefits of trees in the urban forest in the long term far outweigh the costs needed to pay arborists to care for trees.

It has been observed that a grouping of well-placed, healthy trees may help redirect winds and serve as a protective barrier for homes (Figure 7). Communities with a well-maintained urban forest may suffer less tree damage from hurricanes than those without maintenance. Having an active management program reduces the losses from winds and establishes a restoration plan when damage does occur.

Factors to Consider When Deciding Whether to Remove or Restore a Tree

After all the safety concerns have been addressed, the most difficult part of responding to a storm is deciding which damaged trees should be pruned and which trees should be removed. The eight items below are interrelated and together will help you determine the amount of care a tree will need after a storm. They will guide the decision of what trees should be removed and which ones can be restored.

Amount of Damage: Trees with more damage will require more work than those with less damage.

What parts of the tree are affected, how much of the canopy is gone, and how big the wounds are will determine the amount of care needed. The larger the wound is in relation to the size of the limb, the more vulnerable the tree is to decay, diseases, and pests. Generally, gymnosperm trees such as pines with 30 to 50% of the canopy damaged and angiosperms such as live oak with 50 to 70% canopy damage might be beyond recovery due to the severity of canopy loss.

Tree Size and Age: Younger and smaller trees will take less time to restore than more mature and larger trees.

Younger and smaller trees survive winds better and suffer less damage than older trees, making them better candidates for restoration pruning (Figure 10). Additionally, older, more mature trees may have accumulated multiple defects (e.g., bark inclusions, cracks, and extensive decay) over the years, often making them very susceptible to damage in storms.

Tree Species: Trees that resist decay are better candidates for restoration than those prone to decay.

Trees that resist the spread of decay into their wood are called good compartmentalizers and are more easily restorable. Examples include live oak (Quercus virginiana), mahogany (Swietenia mahogani), false tamarind (Lysiloma latisiliquum), winged elm (Ulmus alata), and buttonwood (Conocarpus erectus) (Figure 11).

On the other hand, poor compartmentalizers are trees prone to decay, such as African tuliptree (Spathodea campanulata), Hong-Kong orchid (Bauhinia blakeana), redbay (Persea borbonia), laurel oak (Quercus laurifolia), and water oak (Quercus nigra) (Figure 12). These species may become problematic urban trees since large pruning cuts, trunk injuries, and root damage can result in hollows and extensive internal decay in their roots and trunks.

Short-lived species may not be worth restoring.

Every tree species has an inherent life span, and some tree species live longer than others do (Table 1). Longevity should be considered when evaluating whether a tree is worth restoring or should be removed (Figure 13). Usually, short-lived trees do not compartmentalize decay well. Keep in mind that the risk of failure increases with age.

Table 1. Life span of some species in the forest.*

Short-lived (< 50 years old)	Medium-lived (50–100 years old)	Long-lived (> 100 years old)
laurel oak (Quercus laurifolia)	African tuliptree (Spathodea campanulata)	live oak (Quercus virginiana)
red bud (Cercis canadensis)	paradise tree (Simarouba glauca)	sweetgum (Liquidambar styraciflua)
bottle brush (Callistemon spp.)	red maple (Acer rubrum)	southern magnolia (Magnolia grandifolia)
Hong-Kong orchid tree (Bauhinia blakeana)	gumbo limbo (Bursera simarouba)	bald cypress (Taxodium distichum)
jacaranda (Jacaranda mimosifolia)	sea grape (Coccoloba uvifera)	Mahogany (Swietenia mahogani)

View Table

Tree Health: Healthy trees will recover better after storms than unhealthy ones.

Decay, a major cause of tree failure, is caused by fungi that weaken wood as they grow. Cracks, seams, abnormal swelling, cankers, dead branch stubs, and large, older wounds suggest internal decay and increase the likelihood of tree failure in wind. Decay is often present without obvious signs (Figure 14).

Mushrooms at the base of the tree trunk can be the sign of Armillaria or other fungi that can decay roots and create unstable trees (Figure 15). Root rot can be identified with careful, regular inspections by qualified arborists.

Previous Cultural Practices: Poor pruning practices make trees susceptible to failure and breakage.

Removing large branches results in large pruning cuts that can serve as entry points for fungi that begin the decay process (Figure 16). Topping is a poor pruning practice that should be avoided. Sprouts that grow from topped trees are poorly connected to the cut stub, making them susceptible to breakage in storms (Figure 17).

Poor root management practices will affect tree stability

The importance of root integrity and health cannot be overemphasized. In addition to absorbing water and essential elements, roots anchor the tree. If roots are damaged in any way, the likelihood of failure increases (Figure 18). Construction activities that damage structural roots and trunks can result in decay and be the reason a tree blows over more than a decade later.

Site Conditions: Tree need adequate soil space and good soil properties to be stable.

Trees with root systems confined to relatively small soil spaces are not as stable as trees allowed to develop more extensive root systems. Soil compaction, shallow soils, hardpans, and a high water table restrict roots to shallow depths and can result in unstable trees (Figure 19).

Poorly located and/or chosen tree species may not be worth restoring.

The importance of selecting the right tree for the right location has been greatly stressed, and yet selection of inappropriate trees is one of the most common mistakes observed. For example, white oaks (Quercus alba) can grow to 100 feet and develop wide-spreading crowns and numerous horizontal branches and consequently are a poor choice for planting near utility lines.

If a tree is in the wrong place, such as a tall tree under a power line, or if it is an undesirable species for the site, significant damage may justify removal.

Cultural Value: How valuable the tree is to you and the community will determine the amount of restoration effort needed.

In addition to the economic and ecological values that trees provide to the owner and community, the tree in question might be a memorial tree, or it may have a historical significance, or some other cultural attribute associated with it (Figure 20).

When to Remove a Tree

There are situations when a tree requires removal after safety concerns have been identified. Remember, the priority is to remove trees that represent an unacceptable risk to people and property. A qualified person knows what to look for at the root level, along the trunk, and the condition of branches.

1. The lower main trunk is cracked or broken

Trees with cracks in the main trunk and branches are very dangerous, since limbs with this type of damage are not well-secured to the tree. Cracks that go well into the trunk (Figure 21) will not close and represent a severe defect that makes such trees a high risk in the landscape.

B. A large stem has split from the tree

Figure 22 shows a tree that requires the split stem to be removed. The remaining stem might need to be removed because of the large trunk wound. Notice the dark area at the top of the split—it is a bark inclusion where the two codominant stems joined. Bark inclusions are weak unions between branches and are very susceptible to breakage.

C. The tree is leaning towards a target

If a leaning tree is likely to fall on a person, building, power line, roadway, or other valuable target, it should be removed immediately after the storm. However, all leaning trees should have their roots carefully examined for breakage, exposure, or lifting out of the soil (Figure 23). Pay close attention to leaning trees with unbalanced canopies, cracks in the trunk, and bark inclusions.

D. The remaining tree structure is highly susceptible to breakage

The tree shown in Figure 24 should be removed! It suffered major structural damage, and the remaining tree structure is compromised. All the mass is on one side of the tree, and the trunk is very weak because of the splitting.

E. The major roots are severed or broken

Fallen or leaning medium-aged and mature trees might indicate a severed root or major root breakage. Once cut or broken, these roots will not reconnect well into the soil and are unlikely to develop the root structure needed to keep the tree erect. The reason for that seems to be that severed large-diameter roots do not regenerate new roots as well as small-diameter roots (one-inch diameter or less).

F. Large limbs are broken

Remove trees with most of the canopy damaged due to large-diameter (greater than 8 inches) branch breakage. Trees with small-diameter broken branches have a better likelihood of responding well to restoration (Figure 26).

G. Stem girdling roots are causing dead spots and cracks in the trunk

Roots circling and compressing the trunk are often referred to as stem girdling roots (SGR’s), and tree death could occur when the root encircles most of the trunk (Figure 27). Trees with SGR’s and cracks in the trunk will be less stable than trees without these characteristics and should be removed.

When to Restore a Tree

Even after experiencing high winds, many trees can be restored. However, only restore trees with major limbs, trunk/s, and roots intact (Figure 28). To be a good candidate for restoration, a tree should have no cracks in major limbs or the trunk, no decayed wood, and no bark inclusions. Roots should not be exposed, lifted out of the soil, or girdling the trunk. Make sure the branch and trunk structures were good prior to the storms.

The following are general guidelines that can be considered when evaluating a tree for restoration pruning.

1. Trees are young

Young trees less than 10 inches in diameter make good candidates to restore because there are fewer branches to prune, the canopy is closer to the ground, and they can tolerate having more of their canopy removed than older trees (Figure 29).

B. The canopy is defoliated

Trees that lose their leaves in a hurricane usually are not dead. Many trees generate new foliage in the weeks following the storm*. Research has shown that for some species, such as gumbo limbo and live oak (Figure 30), defoliation is usually a strategy for survival since it reduces wind resistance. Defoliated trees that were healthy before the storm with no major branch breakage require no special treatment. Waiting and giving time is the best treatment for this type of damage. Avoid applying fertilizer or other chemicals, except for an identified reason.

C. Trees and palms that were inundated with salt water often lose leaves due to root damage. In this case, trees need to be irrigated to wash salt through the soil.

Many new sprouts will eventually emerge on hurricane-damaged trees. Some trees wait to produce new foliage the following spring. Sprouts should be allowed to grow because they provide the energy the tree will need to recover (Figure 31), and they can be pruned later.

*Note: Some species, such as pines, may not recover their foliage after hurricanes.

D. Small branches are broken or dead

Trees with small broken or dead branches (less than 4 inches in diameter) can easily be pruned from the canopy and have a good chance of recovering. Trees with small branches have a better chance of recovering than large-diameter branches (greater than 8 inches in diameter). If small, codominant stems are broken in the upper canopy without damage to the main trunk, the tree can also be restored.

E. Most of the canopy is damaged in a decay-resistant species

Trees that resist decay well can lose much of their canopy and still recover from a storm. Even with ¾ of their small branches (less than 4 inches diameter) broken or removed by a hurricane, many decay-resistant trees can be restored.

F. Some major limbs are broken in decay-resistant species

Many species good at resisting decay after they are wounded can be restored even with some major branch breakage.

G. Leaning or fallen trees are small or recently planted

Trees that have a trunk diameter smaller than 4 inches should be stood up as quickly as possible to prevent roots from drying out (Table 2.). Such small trees have a better chance of developing the proper root structure to keep them firm in the soil than bigger trees.

Recently planted trees can be uprighted at any size because they usually do not have large broken roots (Table 2). These trees should be treated as new plantings and staked with the help of a professional.

Assessing Pines

Pines are very sensitive to wind damage. Pines can snap, uproot, or lean after storms. A pine still standing after a hurricane may have internal damage that is not visible. Before deciding to remove or restore, wait and see if the tree lives, considering these points:

• Pines often die over a period of 6 months to 2 years after windstorms.
• Some may remain green for a year or even longer, then suddenly turn yellow (Figure 34) and progress to brown needles in a very short period.
• Pines with all brown needles are dead and should be removed.
• Monitor pines carefully for insects. Weakened pines may be more susceptible to beetles and diseases.

Assessing Palms

Palms grow differently from other trees. The growing point of a palm is at the top of each trunk, surrounded by leaves (fronds). All fronds originate from this one point (bud). If the bud is severely damaged or killed, new leaves fail to develop, and single-stemmed palms will die. On multi-stemmed palms, the undamaged trunks could recover if their buds were not damaged. If the trunk is snapped in half, the palm is dead. However, for palms left standing, the bud is often not accessible, making it difficult to determine whether it is damaged. For these palms, follow these guidelines:

• Allow at least 6 months for palms to put out new growth. New leaves may be stunted, discolored, or abnormally shaped.
• It may take 1 to 2 years or more before palms appear normal with a full canopy.
• Irrigate 3 times a week for 6 weeks if there is not sufficient rainfall; longer if drought persists.

Final Considerations

Right after a storm, it is important to sort trees into priority groups, acting immediately in situations that require urgent attention and selecting trees to be monitored and treated later. Remember that even though hurricanes can be devastating to communities and urban forests, not all storm-damaged trees need to be removed, and many trees can be treated and saved.

When assessing damage, think about it in terms of tree function and your objectives. Management actions will depend on observing the interrelated points below when deciding what trees to remove or restore:

• Soil space and soil properties
• Tree health, size, and age
• Previous cultural practices
• Previous tree structure
• Amount of damage

Always observe safety procedures. Storm damage cleanups are extremely dangerous, even for professionals. Hire a qualified professional such as a certified arborist to help with post-hurricane recovery and to implement a restoration pruning program.