As spring approaches, melting snow and increased rainfall are common in many regions. With climate change contributing to more intense precipitation in certain areas of the U.S., flooding is becoming a more frequent concern. This raises important questions: “How does flooding impact trees?” and “What steps should be taken to help waterlogged trees recover?”

Here’s a guide to understanding flood damage symptoms in trees and shrubs, and how you can assist them in bouncing back after being waterlogged.

Identifying Flood Damage Symptoms

Flooding can affect trees in various ways, depending on the timing, duration, tree species, and their pre-existing health. When trees are flooded, soil conditions shift, oxygen supply to roots is interrupted, and trees become stressed, making them more vulnerable to pests and diseases.

Some signs that a tree has suffered flood damage include:

• Yellowing Leaves: Also known as chlorosis, which is often followed by leaf drop.
• Smaller Leaves: New growth may be stunted, resulting in smaller-than-normal leaves.
• Premature Fall Coloration: Leaves may change color and drop earlier than usual.
• Crown Dieback: The upper part of the tree may begin to die.
• Shoots on the Main Stem: New, small shoots might emerge from the trunk.
• Changes in Seed Production: Flooding can lead to either an absence of seeds or an unusually large seed crop in subsequent years.

Can Waterlogged Trees Be Saved?

The timing of a flood is crucial to determining whether a tree can recover. Trees are particularly vulnerable to flooding damage in late spring, right after their initial growth flush, and during the summer growing season. If flooding occurs during the dormant season or early spring when trees are not actively growing, and the water recedes quickly, the damage is often minimal. However, flooding during the active growing season, especially in warm weather, can lead to significant, long-term harm to trees and shrubs. While some species, like baldcypress and water tupelo, can withstand prolonged flooding, others are much more sensitive and can suffer severe damage or even die.

The Impact of Flooding on Trees

Flooding can have several negative effects on trees, including:

• Reduced Growth: Trees that are moderately flood-tolerant may experience reduced growth in height and diameter, while non-tolerant species may die.
• Oxygen Deprivation: Flooded soils prevent air from reaching tree roots, disrupting root respiration and causing root death.
• Soil pH Changes: Flooding can alter soil pH, increasing it in acidic soils and decreasing it in alkaline soils.
• Root Exposure: Erosion caused by flooding can expose tree roots, making them more susceptible to damage or uprooting.
• Sediment Accumulation: Sediments deposited by floodwaters can lead to basal rot, unexpected rooting, and girdling roots.
• Increased Pest Activity: Stressed trees are more likely to be attacked by boring insects and to develop root rot diseases during and after flooding.

Steps to Help Trees Recover After Flooding

Healthy trees are more likely to survive flooding, but they still need careful attention to recover. Here are some steps you can take:

1. Remove Excess Sediment: Once the ground is stable, carefully clear away any sediment that has accumulated around the base of the tree, taking care not to damage exposed roots.
2. Fill Eroded Areas: Use soil that matches the existing soil’s composition to fill in low spots, incorporating at least 5% organic matter by weight.
3. Replace Washed-Away Mulch: Mulch helps retain soil moisture and prevent erosion, so replace it where needed.
4. Monitor for Stress: Keep an eye on flooded trees for signs of stress and take action as needed.
5. Fertilize Appropriately: Use soil tests to determine if fertilization is necessary and apply accordingly.
6. Prevent Root Rot: Take preventative measures to protect trees from root rot diseases.
7. Improve Drainage: Where possible, enhance drainage around your trees to prevent future flooding issues.
8. Leach Salt from Soil: If your soil has been flooded with saltwater, irrigate with fresh water to flush out salts, applying no more than 2 inches at a time.
9. Get Professional Help: Have a certified arborist assess any trees near structures or high-traffic areas to ensure they are safe and stable.

Choosing the Right Trees for Flood-Prone Areas

When planting or replacing trees in areas prone to flooding, select species that can tolerate excess water or help absorb additional soil moisture. Consulting with a certified arborist can also provide valuable guidance on how to care for trees after a flood, ensuring they receive the attention and care needed to recover fully.

For more information on managing oversaturated soil and caring for your landscape, reach out to your local tree care professionals.