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Serving: NE
2019 Midwest Flood
flooded field
WATERLOGGED: These trees were swamped in floodwaters from the Missouri River in 2011. Farmers and ranchers should assess damage and keep up on preventative maintenance on flooded trees.

Assessing tree resources after a flood

Farmstead Forest: As the floodwaters recede, how did the water affect your shelterbelts?

In the Great Plains and throughout portions of the Western U.S., tree planters normally are concerned about drought conditions when there isn’t enough water and precipitation to sustain our rural trees.

For many regions this year, however, the opposite is true. Floodwaters, beginning with spring thaw in March, have swamped shelterbelts and trees anywhere near a waterway.

From debris hanging in tree limbs to complete removal of large portions of our rural tree landscape, flooding has done much damage to our forest resources — along with the loss of life, livestock, farms and ranches. As disasters go, this has been complete devastation in many areas.

Gleaning tips from my own experiences, as well as resources across the Great Plains, I’ve picked up a few recommendations that may be useful this summer as you assess your rural tree resources.

Flooded trees are under stress. Roots, trunks and branches are softened and strained. Trees may be leaning because of damage from ice and water. Debris may be pulling branches down, even cracking limbs and trunks of the trees over time. Stressed, flooded trees may be open to additional disease and insect pressure this spring and summer. 

If flooding occurs during the growing season, that is usually more harmful than flooding during the dormant period. Flash floods that only expose trees to water for short periods are not as harmful as long-term flooding that lasts for days and weeks.

Most trees can handle a little water, but continued flooding or recurrent flooding that keeps the soils waterlogged takes a toll.

These waterlogged soils have reduced oxygen supply, which results in injury to trees in that environment. All kinds of symptoms can result, such as growth inhibition, leaf chlorosis or yellowing, smaller leaf size, sprouts along the trunk, crown and branch dieback, and defoliation.

Indirect effects from flooding also hurt trees, such as heavy sediment deposits that also reduce soil oxygen, along with deposits of toxic compounds through floodwaters.

Trees in the way of huge ice chunks and debris suffer from damage to the trunk and branches, as well as erosion around the base that uncovers roots and removes soils that serve to maintain the foundational roots of the tree.

Some species such as red maple, black willow and bald cypress are relatively tolerant to waterlogged soils. But species such as sugar maple, Colorado blue spruce and even Eastern red cedar are considered intolerant to having their roots wet for too long.

Still others such as river birch, Eastern cottonwood and hackberry have intermediate tolerance.

Structural problems with flooded trees need to be addressed by a professional arborist as soon as possible to prevent falling trees and limbs around the farm and fields. Farmers also should keep watch during this growing season for disease and insect issues that may arise on flood-stressed trees.

While the best plan for flooded trees is to keep up on preventative maintenance and tree care, it may take patience over the long haul to truly assess damage from this year’s excessive flooding.

If you are looking for good resources on helping flooded trees, visit flood.unl.edu/horticulture.

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