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

Storm Damage Often Reveals Rotted Trees

June 17, 1999

When storms like last week bring lots of wind, tree damage 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. Typically these trees have wood rot.

When a large limb or tree comes crashing down, inside portions of that limb or trunk are usually revealed to be 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.

The puzzling part of this is the tree that came down had plenty of foliage and appeared to be fine. But after it blew down, the wood rot damage becomes very visible. Keep in mind the vascular system of trees is just under the bark, so trees with wood rot can appear fine because water and nutrient exchange continues between the leaves and the roots. However, as wood rot fungi invade the heartwood, or center wood of trunk that is actually dead wood, trees become structurally weakened.

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 last week, 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. As discussed a few weeks ago, 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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