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Why is My Oak Tree Losing Bark Update

Since the original posting of the “Why is my Oak Tree Losing Bark?” post last year, the question continues to be raised in Tennessee and around the country.  The original post covered one possible explanation – the Smooth Patch Disease of White Oak which is just a fungus that feeds on bark but does not otherwise harm a healthy tree.

Hamilton County Extension Agent Tom Stebbins provides some additional observations below.

Why is so much bark falling off my trees?

This is an observation I heard from many homeowners last year and now again this year.  Some people made their own diagnosis and blamed the pile of bark on squirrels or birds.  Squirrels might explain some of the problems. Incisors of squirrels can grow up to six inches per year.  So, they are constantly chewing and gnawing to keep their teeth short. It would take an army of squirrels to do the damage reported.  Some people report they don’t have many squirrels but still a lot of bark falling around the trees.   Birds could also be looking for insects. Some bark would come off by their pecking.  Again, it would take a fleet of birds to do the reported damage.  There would be bird droppings all over the base of the tree.

There may be multiple reasons for bark flaking.  The primary and consistent cause for bark flaking is from natural tree growth.

Most trees have a growth spurt in the spring. When moisture is plentiful and the sap is rising to support newly formed leaves, tree trunks expand from the living cambium cells. This is a ring of cells just under the bark.  As the tree expands in diameter and circumference, the inflexible, dead cells of the bark are pushed further out and are not able to stay attached to the tree trunk. Thus the bark exfoliates.  This is a natural process that occurs every year.  In some years and in certain trees there may be more growth.  We have had several years of fall drought which have stunted growth.  Now abundant fall and spring rains have caused some trees to have a growth spurt.

The same process occurs in all trees.  Some trees like red oak have thick, tighter bark. This bark is more corky and flexible. This bark is able to hang on the tree, retain more flexibility, and exfoliates much more slowly than those with thinner bark. Trees like white oak have thin, flaky bark.

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