I noticed this shallow hole in the base of my Catalpa. Should I be worried about it?
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The Utah State University forestry extension article provides information on a wounded tree “When a tree is wounded, it sets up defensive walls against the invasion of decay fungi and other microorganisms. The vessels near the wound are plugged with gums, resins, and chemicals that resist the spread of decay. The living tissues outside of the wounded area will then begin to form a callus layer in an attempt to close the wound” Tree Injury
The Catalpa tree trunk looks healthy. If you know what caused the hole and its not rot or disease and you feel comfortable with the hole in the trunk you could just let the tree be. In time the tree will grow larger at the base overcoming the hole. The Catalpa will grow 40 to 60 feet tall. Catalpa Tree Information
The Gardening Know How article provides details on tree trunk holes. The best thing is not to do anything if its not affecting your tree. Read more at Gardening Know How: Filling Holes In Tree Trunks: How To Patch A Hole In A Tree Trunk Or A Hollow Tree.” Tree Trunk Hole