Why trees topple and what you can do to reduce the risk

A pedestrian touches a fallen tree that crushed a parked car in New York City. New York. (AP / John Minchillo)

Serious injuries, fatalities and major property damage can occur when trees come crashing down during high-wind and heavy-rain events.

The most common contributors to trees falling over during high winds are soggy soil and a compromised root system.

Aside from a few broken branches, most healthy trees can weather brief periods of high winds and heavy rain from thunderstorms. However, in situations where the ground is saturated, tree roots can lose grounding in the soil and an entire tree can come crashing down.

Amid heavy rains and often during the springtime, a surge of fluid, or sap, is drawn up into the canopy making the tree top-heavy and prone to toppling.

A large and healthy root system is crucial for a single tree, a small group of trees or a line of trees to survive a high wind event or fluctuations in sap levels.

It's not unheard of for healthy trees to become top-heavy during or shortly after long-duration rain events from the weather elements, but other less obvious factors can also lead to a tree becoming top-heavy and falling.

In some cases, tree limbs and roots may grow a certain way to accommodate for prevailing winds. Should a storm hit these trees with strong winds from a different direction, those trees could fall.

Other factors that can lead to trees toppling involved methods used at the time of planting and other man-made elements that encroach upon or interfere with a tree's natural growth pattern.

Poor planting techniques, infrastructure crowding and root damage impact root health and will negatively affect the strength of a tree over time, according to the Sacramento Tree Foundation.

Trees planted at the proper depth in an open area and in well-drained soil will fair much better in high winds than when planted in often wet soil or where roots are restricted or cut by roads, sidewalks, driveways, and building foundations.

Soil type, disease, insect infestation, lack of maintenance and over-watering are also likely to increase the risk of a tree falling during a storm.

Tree limbs: Proper pruning is essential for avoiding damage

Trees that have been trimmed for utility lines or for infringing on dwellings may become unbalanced.

The limbs of older trees require periodic professional maintenance. It is essential to keep the canopy balanced with strong, healthy branches.

The leading causes of large tree limb failure during strong winds are improper pruning, disease and species of tree.

Many property owners can do more damage to a tree in the long run by trimming the wrong branches. For most large shade trees, a single main trunk, or leader, is best.

The strongest tree limbs are those that are not crowded and emerge from the main trunk close to a 90-degree angle as opposed to growing in direction that creates a narrow V-shape.

Dead or diseased branches should be promptly trimmed. If a large dead or diseased limb has to be removed on one side, another branch may need to be removed on the other side.

A licensed arborist will have the skill to help keep the tree healthy in the short term and for years to come.

Some tree varieties just don't hold up

Certain varieties of trees are more storm-damage prone than others due to a weak limb and root structure.

Consider what the tree may look like 10 to 20 years down the road. If a branch breaks or if the whole tree falls, what will it hit?

According to The Morton Arboretum, one tree species that experts recommend property owners avoid planting is the silver maple. The silver maple's rapid-growing nature and narrow-V limb structure also make it highly susceptible to major damage and failure during windstorms and early- and late-season heavy wet snowfall.

An employee of the public works department tries to remove a tree branch that fell on a house during a storm in Newburgh, N.Y., Wednesday, May 16, 2018. (AP Photo/Seth Wenig)

This towering, inexpensive and untidy tree is also considered to be invasive in some areas. The mature silver maple, which can reach heights of 50 to 70 feet, also releases hordes of rain gutter-clogging seed pods, or spinners.

Other trees on the poor-choice list for longevity and storm-weathering capabilities include the bradford, or callery, pear and the weeping willow.

Property owners are always advised to do some homework before buying trees to plant in landscaping projects.

For more safety and preparedness tips, visit AccuWeather.com/Ready.