Trees and Wind: Preparing for Storm Season
From light breezes to powerful storms, trees are exposed to the full range of wind forces that accompany all types of weather. This couldn’t be more true in Nashville, TN, which has seen its share of tornadoes and severe wind gusts in recent years. Late winter and early spring tend to be the windiest time of year for Music City, so it’s crucial to understand how wind affects trees and what you can do to minimize potential damage (to your trees and your property).
As we explore in this article, wind isn’t inherently bad for trees; despite the destruction caused by strong winds, wind, more broadly, is critical for tree development. Wind helps a specimen become both flexible and strong, while intentional pruning shapes a tree into its sturdiest form. By working with a tree’s natural disposition, we’re able to reduce the risk of hazards and tree loss while maintaining the local canopy in as hardy and resilient a condition as possible.
Tree Resilience in Wind
Resilience is about gaining strength from stressors, and this is illustrated wonderfully by a tree’s interaction with wind. As trees grow, wind pushes against them, making them sway and bend as the air moves around. This movement actually benefits trees in several ways:
Root Gripping: When a tree is exposed to wind, it rocks back and forth, and the roots respond to the stress. They reach down into the ground and outward in the topsoil, which anchors the tree firmly in response to the movement of the upper portion.
Base Strengthening: The tree’s trunk is its stem, connecting the roots to the crown. As the base of the trunk strengthens and widens as it bends and rocks in the wind, the wood at this junction becomes particularly resilient, allowing flexibility while minimizing the chance of snapping.
Branch Strengthening: As a tree crown twists and sways in the wind, the joints of the branches develop the same type of “reaction wood” that is found at the base of the tree trunk, which strengthens the connection and allows the tree to bend and resist forces that might cause breakage.
Together, these natural responses help ensure the tree's stability. Knowing how a tree responds to the wind helps tree care providers make decisions about how to best manage trees, and there is much ongoing research to better understand the interactions between trees and wind.
Wind and Trees in the Environment
In nature, trees tend to grow in groups, which reduces the impact of high winds on individual trees by creating a dense blockage in the landscape. They also grow tall and thin when in close proximity to other trees. On residential property, however, tree specimens tend to be much more isolated, and they’re more directly exposed to the force of the wind. Spacious planting can result in wide branches and a strong base, but the shape of the tree can create certain hazards if the branches aren’t pruned properly as a tree grows.
How Can Strong Wind Damage a Tree?
Research has shown that the structural shape of a tree influences how it stands up against windy conditions, making a good pruning routine essential for the safety of neighborhood trees. Overgrown branches, weak or shallow roots, and lopsided growth are some of the conditions that can result in a tree at risk of damage in high winds. Outcomes might include:
Broken branches
Trunk snapping
Uprooting
A tree whose branch connections are weak, either due to co-dominant leaders (where there are two main trunks rather than a single one) or overgrown crown branches, is more at risk of breaking in high winds. On the other hand, over-pruning a tree can also make it unstable: too much thinning of the crown or removing too many lower limbs to “elevate” the crown will reduce a tree’s ability to tolerate wind loads. “Butt rot,” when the base of the tree is damaged from fungi, makes a tree more vulnerable to falling over in a storm. Certified arborists are trained to consider these issues when inspecting and caring for trees.
A big, weak tree becomes a danger for people and property and can result in real damage if a large branch or whole tree comes down in a storm. Weak trees might be able to be stabilized by a certified arborist with cables or bracing, while other times, they may need to be removed. The best way to prepare trees to grow into robust and sturdy specimens is with proper pruning from the time of planting and throughout their lives.
Landscaping for Wind Tolerance
When certified arborists prune a tree, they focus on certain characteristics that help it stand strong:
Height: Making sure a tree doesn’t get too tall too quickly will help it grow a strong base to support its mature height. Leafy tree crowns catch the wind load far above rooftops, which pulls at the tree’s base and roots as it sways, so a good grip and ability to withstand bending are important to develop.
Density and Form: Arborists carefully shape a tree by removing small branches and leaving the biggest, strongest ones. Symmetry is important for stability, so arborists will try to keep the tree’s shape as even as possible to balance it on all sides.
Root Health: A tree with strong, even roots will hold in place better than a tree whose roots are weak, shallow, damaged, or lopsided. In wet storms, soggy soil can loosen, making gusts of wind more able to uproot a tree.
When a young tree is planted, arborists may stake the small tree during the windiest parts of its first few years to be sure that it doesn’t bend too much or topple over in strong winds. However, even very young trees are often left to sway in the wind to build their natural tolerance, which will be important as they mature.
Trees in the Nashville Climate
When maintaining trees for wind tolerance, well-pruned trees will be the sturdiest and most resilient. While the most catastrophic storms, such as those producing tornadoes, may bring down even the strongest of trees, a good maintenance routine will increase a specimen’s chances of survival in all types of weather. A strong, mature specimen will produce important ecosystem services and health benefits that have effects for many years.
Some of the sturdiest trees are those with wide trunks, buttressed root flares, and deep grips into the ground, such as oak, bald cypress, and many pine trees. Native species are adapted to tolerate the winds and storms of the most turbulent Tennessee weather and should be planted across the Nashville landscape.
These species and many others can be purchased through NTCC’s tree sale! Nashvillians can also volunteer to help us plant trees or donate a tree for us to plant. We are very thankful for the financial donations that we receive from residents and businesses, which are a major source of funding for our canopy care activities.
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