Other Threats


Trees are adapted to withstand most wind events but strong winds can be a serious threat to a tree's structural integrity.


Tree structure can support heavy loads but there is a limit to the weight capacity of branches that are periodically tested by snow and ice. 


Storms can expose trees to a combination of the most destructive atmospheric stress agents: heavy rains, saturated soils, strong winds, snow, ice, hail, and/or lightning.


Trees need, on average, 1 inch of water per week and some trees can lose nearly 400 gallons of water on a hot summer day through transpiration. Drought symptoms will first appear on leaves in the upper crown.


Tree roots require oxygen for cellular respiration. During floods, roots become starved of oxygen which can severely damage root systems and lead to decline or death of the tree.


Hail can damage tree leaves by bruising, shredding, or stripping them from the tree. Wounds caused by hail can often serve as infection points for many diseases


Trees are ideal targets for lightning strikes. When a tree is struck by lightning, the damage can vary from vertical stripping of bark to total tree explosion.


Heavy rains can damage leaf tissue or cause minor defoliation. Prolonged periods of leaf wetness can increase susceptibility to certain diseases such as anthracnose or needle cast. Splashing rain can transmit pathogens.

Frost and Freezing

During freezing temperatures, ice crystals from inside of plant cells that rupture the cellular membrane, resulting in death of frozen tissues. Early frosts in the fall or late frosts in the spring can catch a tree off guard.


Intense heat can easily damage the thin layer of vital tissue just under the bark of a tree. Radiant heat from surfaces such as asphalt or dark rocks can 'cook' the living cells of the vascular system.

Air Pollution

The foliage of trees, particularly hardwoods, is very susceptible to air pollutants including sulfur dioxide, fluorides, and oxidants such as ozone. The pollutants can be absorbed by leaf tissues and can kill cells within a few hours or days.


Intense fires can easily damage the vital tissues right under the bark of trees. It can also kill buds, foliage and near surface roots further stressing tress and making them susceptible to secondary stress agents such as insects.

Mechanical Damage

Mechanical damage refers to the physical injury of a tree and is a term usually reserved for those injuries caused by people or animals. Repeated injuries can lead to decay, disease, localized dieback or mortality.

Root Injury

The vast majority of a tree's root system is within 24 inches of the soil surface. Because of this, roots can be easily damaged by human activity. Lawnmowers, soil compaction and site disturbance can damage roots  as well as make them more susceptible to pathogens.

Herbicide Damage

Symptoms of herbicide damage can vary with the type of herbicide and formulation used, time of year and the plant species. The most common symptoms include chlorosis, dieback, epicormic sprouting, abnormal growth patterns, stunting, wilting, cupping/curling and death.