Water is great for trees — except when it comes all at once. Flooding caused by heavy rains in Kansas has prompted concern of over its impact on the state’s trees, according to a story in the Salina Post. However, the advice given in the story is helpful to any landscaper or arborist working in any region of the country affected by recent flooding.
“There are three major concerns when it comes to trees and too much rain,” Ryan Armbrust, a forest health and conservation forester with the Kansas Forest Service, told the reporter. “First is the immediate destabilization of the tree caused by saturated soils or soil erosion. Second is the deposition of significant amounts of silt on the root system. Third is the duration of flooding.”
Armbrust warns that trees that suddenly begin to lean or even fall over due to the force of high water, wind or soil erosion should be treated as a hazard if they are near people or structures. He suggests that an assessment by a certified arborist should be made, especially for larger trees.
The forester also suggested removing the silt deposits. “If more than an inch of silt is deposited, then some careful removal of that silt will benefit the tree.” Root systems that are buried under heavy layers of silt have a reduced ability to exchange gases. This can negatively affect a tree.
How long the flooding and soil saturation lasts will have a direct impact on a tree’s ability to recover, the story says, but this will vary with the species. Trees that have been inundated for less than a week should recover, especially if the water is flowing rather than stagnant.
Tree species that are most sensitive to short-term flooding include redbud, walnuts, mulberry, upland oaks, most pines and conifers such as spruce and Eastern red cedar.
Honey locust, elm, birch and lowland oaks are among the more resilient and flood-tolerant types of trees, able to survive even after weeks of flooding.
“The most tolerant trees include typical riparian forest species such as maples, pecan, hackberry, persimmon, ash, sycamore and cottonwood,” Armbrust is quoted as saying. “Bald cypress and willow are perhaps the most tolerant of all.”
The story stresses that regardless of species, some care must be taken to help all trees in flood areas maintain vigor and reduce stress.
“Almost all species will have some dieback of the root system due to lack of soil oxygen, reducing the tree's ability to take up water later in the season, so supplemental irrigation in the hot, dry days of summer will help your trees continue to flourish after the flood,” Armbrust stated further.