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How Minnesota trees can survive floods

Minnesota is coming off from one of the rainiest and coolest Aprils in recorded history. According to climate summaries, April 2022 was among the top ten coldest in Minnesota’s history and average temperatures were 6 to 8 degrees F below normal.

Counties in the northwest and north-central part of the state also saw especially high precipitation levels compared to other regions in the state. While snowmelt this time of year always brings concerns with flooding in regions such as the Red River Valley, the risk of flooding is present in several areas of Minnesota.

With the increased precipitation and risk of flooding, what does this mean for the survival and growth of trees?

Tree responses to flooding

Many forested ecosystems are adapted to flooding and fluctuations in the water table. Other trees and forests cannot survive flood conditions for even a short period of time.

Trees and forests along floodplains and near rivers are well adapted to tolerate waterlogged soils to a certain extent. Many landowners have seen the damage that beavers can do in flooding areas, resulting in large numbers of trees that are not tolerant to flooding being killed.

If trees are not tolerant, flooding can suffocate roots and kill trees. The degree to which flooding impacts trees depends on the species, time of year, and size and health of the trees. Healthy trees require oxygen to survive and thrive. If water occupies air spaces during a flood, the roots of trees are unable to use oxygen.

Flooding for short periods (a few days) in the spring is rarely a serious problem. However,  flooding during the growing season can kill trees in just a few days.

Some of Minnesota’s most flood-tolerant trees include:

  • American elm
  • Black ash
  • Green ash
  • Eastern cottonwood
  • Silver maple
  • Willow
  • Swamp white oak
  • River birch
  • Hackberry

Some of Minnesota’s least flood-tolerant trees include:

  • Sugar maple
  • White spruce
  • Jack pine
  • Eastern white pine
  • Northern red oak
  • Paper birch
  • Basswood

How to deal with flooding on trees

There aren't many actions you can take to stop the effects of flooding. Instead, if an area is flooded, it is best to continue to monitor the tree for its health throughout the growing season.

Trees showing signs of flood damage may break bud and leaf out later than other trees. As spring turns to summer, flood-damaged trees may have leaves that are wilted or appear smaller in size compared to leaves on healthy trees.

Healthy trees should begin growing as floods recede and the weather warms. Continue to monitor the health of the tree throughout the growing season. If you notice the tree is in poor health as the growing season goes on, consult a professional arborist for your yard trees or a professional forester for your woodland.

If you’re planning to plant trees this spring, consider flood tolerance in selecting a species to plant. If you’re in a flood-prone area, plant only tree species that tolerate flooding. To help, a list of our recommended trees for Minnesota by region can be found here.

Matt Russell, Extension forestry specialist

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