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NDSU Photo by Megan Myrdal

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.

NDSU Photo by Dave Haasser

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

Able to withstand one to three weeks

• Black chokeberry
• Silky dogwood
• Honeysuckles
• American black currant
• Eastern arborvitae

Unable to withstand more than seven days

• Juneberry
• Cotoneasters
• Euonymus
• Forsythia
• Cherries, plums, apricots, peaches (genus Prunus)
• Golden currant
• Lilacs
• Yews