Choose trees native to Mississippi for storm resistance

Published 6:00 am Sunday, September 17, 2017

By Bonnie Coblentz

MSU Extension Service

STARKVILLE, Miss. — Hurricanes Harvey and Irma are devastating reminders that storms take a terrible toll on landscapes and proof that some trees hold up better than others.

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Mississippi landscapes must withstand flooding, hot summers, seasonal drought, ice storms, winters that can dip to single digits, a humid and subtropical climate, and high winds from hurricanes and tornadoes.

John Kushla, a forestry professor with the Mississippi State University Extension Service and the Forest and Wildlife Research Center, said native vegetation handles a wide variety of environmental conditions, but some species are able to survive storms better than others.

“Tree species vary widely in their ability to tolerate high winds, and the ability of any individual tree to survive windstorms also depends on its health,” Kushla said. “Some characteristics enable trees to handle high wind.”

Some tree species defoliate during extreme winds, helping them survive by limiting the surface area that catches the wind. These trees include live oaks, flowering dogwoods and crape myrtles. Trees with high wood density or elasticity, such as live oak and longleaf pine, also fare better.

If flooding is the most likely local risk, homeowners can select trees species for their ability to tolerate this threat.

“Tree roots need oxygen, and most trees will not tolerate flooding during the growing season,” Kushla said. “While small seedlings can be covered with siltation from river flooding, mature, vigorously growing trees of tolerant species are best able to abide flooding.”

Bald cypresses, American sycamores, common persimmons, and some oaks and sweetgums are good examples of flood-tolerant trees.

Ice storms present a unique set of challenges to trees. A tree’s ability to avoid ice damage usually lies in its tolerance to ice accumulation.

“Tree species most resistant to breakage from ice generally have strong branch attachment, flexible branches, a low branch surface area and a single main trunk,” Kushla said.

Examples of ice-tolerant species that grow well in Mississippi include bald cypress, black walnut and Eastern red cedar trees.

Kushla warned that just because a tree is storm resistant does not mean it is a good choice for the landscape. For example, the green ash, white ash and fringe tree are ideally suited to withstand storms, but they are susceptible to the emerald ash borer, an invasive pest. The Eastern cottonwood and silver maple are flood tolerant, but their wood is brittle, a disadvantage in storms.

Kushla said the black willow and box elder tolerate flooding but should not be used in an urban setting because their shallow root systems often damage septic or sewer lines.

Bob Brzuszek, an MSU Extension Service professor in landscape architecture, said location is another important consideration when planting trees.

“Typically, where you have problems occurring is when you have trees being placed near utility lines or structures or areas being used,” Brzuszek said. “Have an arborist visit the property to make an evaluation and consider impacts in the placement of trees.”

A key to having a successful tree in the landscape is making sure it has good roots.

“Provide root stimulators or fertilizers that help promote those roots, and use mulches to keep the roots from drying,” he said. “Saturated soils make trees prone to being blown over by the wind, but healthy roots make a healthy tree.”

Brzuszek urged homeowners to have a replacement strategy for existing trees.

“We can’t control what a storm will do, but we can control the next forest, and we can plan what the next tree will be,” he said. “Replacing a mature tree takes years. Plant some understory trees so if something does happen, you’re not waiting 30 years for another tree to make an impact in your landscape.”