A storm-resistant landscape design and consistent tree health monitoring can save cities and property owners time and money.
"Well-designed landscapes are easier to maintain and reduce the risk of damage from a fallen tree or limb," said John Kushla, a Mississippi State University Extension Service forestry specialist and associate research professor in the Forest and Wildlife Research Center.
Good design helps trees weather storms more easily.
"Consider planting in groups if space allows," Kushla said. "Instead of planting one large tree, use several small ones. A group planting withstands a storm better because the closed canopy deflects winds."
The most important step in designing any landscape is to make sure the right trees go in the right spaces, which reduces the chance of property damage.
"Allow enough open space for the adult tree," Kushla said. "An adult tree needs open space that is equal to three times its trunk diameter when mature. A large tree needs 1,000 to 2,000 cubic feet of soil. If the tree does not have adequate space, the roots could cause old or improperly constructed sidewalks, parking lots and streets to crack. Damage or injuries caused by those impaired structures become the municipality’s liability."
Brian Templeton, an Extension associate professor in MSU’s Department of Landscape Architecture, agreed.
"It is especially important for municipalities to properly plan their landscaping," Templeton said. "Municipalities can be liable for personal injury or property damage caused by the failure of trees on public property, especially if the trees are not properly managed."
When considering the location of trees, it is also important to pay attention to the condition of the soil. The mineral content and the amount of pore space in the soil are critical to the health of the tree. The ideal soil is made up of 50 percent mineral solids, 45 percent pore space, and 5 percent organic matter and organisms.
"Compaction is the enemy," Kushla said. "It affects the ability of the tree to absorb water and develop its root system."
For municipalities, suspended sidewalks, porous paving and structural soil can alleviate the problem of compaction around tree roots. Porous paving materials include crushed granite, gravel, porous asphalt, wood decking and brick-and-sand. Structural soil is a mixture of a medium-large aggregate material and soil, with 20 percent of the mixture made up of soil. All three options allow proper drainage and root formation for trees planted in city settings.
After design, upkeep is the second most important ingredient for storm-resistant landscapes.
"Maintaining the trees saves a lot of time and money," Kushla said. "A regular pruning schedule will eliminate a lot of headaches."
A certified arborist should inspect trees in municipal settings on a yearly basis to keep problems to a minimum.
"Defects are not always visible," Templeton said. "Performing proper pruning and care is the best way to manage a tree. If an arborist is consulted early and a maintenance schedule is followed, pruning becomes less and less work each year. The cost also will be manageable."
Homeowners benefit from the same basic guidelines as municipalities when choosing trees for the home landscape.
Plant trees at least 20 feet away from houses to avoid root damage to the foundation and driveway, and give the tree enough room to grow to full size, Kushla said.
"As with cities, better landscape design and regular maintenance will improve storm tolerance," Kushla said. "It’s bad enough to weather a storm when the power goes out, let alone having a tree fall on your house."
Both Kushla and Templeton recommend contacting a certified arborist when a damage assessment is needed.
"When a mature tree loses more than 25 percent of its canopy, it may very well go into decline and eventually die," Kushla said. "So, evaluating how much canopy remains is very important. Other tree conditions, such as splits or peeled bark, also need consideration."
For more specific information about landscape planning, contact the county Extension office. For a list of certified arborists, visit the International Society of Arboriculture website at www.isa-arbor.com.