University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Rotted Trees Visible After Storms

July 13, 2000

Storms with significant wind have been common over northern Illinois in the past few weeks. Damage to trees from these storms may be significant. While some smaller twigs and branches are expected, sometimes a large limb or entire tree falls unexpectedly. The tree was green and growing, yet is blown down. This is often due to wood rot.

When a large limb or tree comes crashing down, inside portions of that limb or trunk are often rotten. Internal wood may be soft, dark in color, or completely hollowed-out. Wood rot fungus causes this, and usually enters through wounds to the tree.

Frequently the damaged tree looked fine with plenty of green foliage. Once the limb broke or tree blew over, the wood rot damage becomes very visible. This is because the vascular system, or lifeline, of trees is just under the bark. Water and nutrient exchange continues between the leaves and the roots via the vascular system. However, as wood rot fungi invade the heartwood, or center wood of trunk that is actually dead wood, trees become structurally weakened. This is why they break in storms.

Inspect trunks of trees, in particular large trees near buildings, sidewalks, parking lots, etc. Look for sign of wounds, missing bark, or discolored areas. Certain times of the year, fungal structures, similar to mushrooms, may be visible. This is a telltale sign of wood rot. These trees become potential hazards.

Consider having suspect trees inspected by a certified arborist. Trained arborists can help in assessing the condition of a tree and if it is suspect to be weakened.

Take a good look at larger shade trees in your yard. After the winds of summer storms, broken branches may need to be pruned out. There also may be broken stubs left that need to be pruned correctly. Neglect could lead to wood rot problems later.

Finally, prevent wood rot problems by avoiding damage to the trunk and root systems of trees. Keep mowing equipment away from the base of trunks. Don't dig in the vicinity of trees. Avoid compacting the soil over tree root systems and also don't put fill over roots. Many of these problems lead to injury that in turn leads to wood rot.


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