Title

Helping Flooded Trees and Shrubs

(H1592, Revised April 2021)

File

Publication File:

Summary

Flooding periodically happens in North Dakota. Post-flooding management decisions can help or harm trees and shrubs on their road to recovery. A list of flood-tolerant trees/shrubs, and a list of flood-sensitive trees/shrubs, are provided.

Lead Author

Lead Author:

Joseph Zeleznik, Ph.D., Extension Forester

Availability

Availability:

Web only

Publication Sections

Flooding scene with trees and shrubs submerged

Photo Credit:

Megan Myrdal, NDSU Photo

Symptoms of flood damage

Leaves – discoloration (yellowing), wilting, scorched appearance, early fall color or leaf drop (Flood symptoms are very similar to drought symptoms.)
Branches – dieback of existing branches, sprouting of new branches from the trunk

Determining amount of damage

Water – If the entire tree crown is or was covered with water for any amount of time, the tree likely will die. However, a high amount of oxygen in the water can reduce the damage:
- Fast-moving water contains more oxygen than slow-moving water.
- Shallow water warms quicker and loses more oxygen.
Health of the tree – Very young and very old trees are unlikely to survive; previously healthy trees have a better chance at survival.
Inspection – Use your thumbnail to scratch the bark from a young limb; if you find green tissue underneath, the plant is alive though there is no guarantee that it will recover.
Season of flooding – Floods that occur in the dormant season will not harm trees.

Recovery of flood-damaged trees – reduce future stress

Remove sediment that has accumulated on the soil surface.
Fertilization – Lightly fertilize with up to 1 pound of nitrogen per 1,000 square feet of soil surface.
Pests – Scout for insects and diseases and treat as necessary.
Damaged bark – Remove loose bark and carefully trace around wounds with a sharp knife to remove loose bark; do not use pruning paints or wound sealers.
Remove only dead branches and limbs. Do not top trees.
Recovery – Trees or shrubs may take up to five years to recover.

Photo Credit:

Dave Haasser, NDSU Photo

Tree removal

Flood-damaged trees may fall over in high winds because of weakened root systems and/or saturated soils.
Hire a professional arborist for removing large branches and trees.

Tolerance to Soil Saturation or Surface Ponding During Growing Season

Trees

Often able to withstand more than three weeks

Ash – green, black, Manchurian
Boxelder
Cottonwood
Common hackberry
Willows

Able to withstand one to three weeks

Silver maple
Freeman maples (‘Autumn Blaze,’ ‘Sienna Glen,’ and others)
River birch
Russian-olive
Honeylocust
Quaking aspen
Bur oak
American and hybrid elms
Arborvitae

Unable to withstand more than seven days

Norway maple
Sugar maple
Ohio buckeye
Paper birch
Hawthorns
Black walnut
Apples and crabapples
Mountain-ash
American linden (basswood)
Siberian elm
Siberian larch
Junipers (including Eastern redcedar)
Pines
Spruces

Shrubs

Able to withstand more than three weeks

Redosier dogwood
Willows
Nannyberry
American cranberrybush