November 30, 2010

A tree is not a tooth


J.J. Levison, 1909 in the journal Mycologia, 1(2): 77:
Everyone recognizes the necessity of filling a decayed cavity in a tooth. Everyone knows that the decayed material in the cavity must be removed in order to prevent the destruction of the whole tooth and that the opening must then be filled in order to keep out the further accumulation of injurious substances. Still, there are some who might be surprised to hear of scientific tree "dentistry," or tree filling, although the underlying principles and necessity for such treatment are alike in both human beings and trees.

As recently as 1974, the US Forest Service recommended "shaping the wound into a vertical oval" and applying "commercial tree dressings such as orange shellac or those with an asphalt base."  Proper disclosure: the Forest Service has cautioned readers that the advice in "Your Tree's Trouble May Be You!" might be out dated.

By the 1990s, "tree dentistry" was an increasingly marginalized arboricultural practice.  From "HOW to Prune Trees," a US Forest Service pamphlet published in 1995:
Wound dressings will not stop decay or cure infectious diseases. They may actually interfere with the protective benefits of tree gums and resins, and prevent wound surfaces from closing as quickly as they might under natural conditions. The only benefit of wound dressings is to prevent introduction of pathogens in the specific cases of Dutch elm disease and oak wilt.
The concept of tree injury compartmentalization developed by Alex Shigo Ph.D. was the primary factor in eschewing filling tree cavities.  From "How Trees Survive After Injury and Infection" written by Dr. Alex Shigo for the US Forest Service (undated):
The problem with wound dressings and with many other tree treatments center about the desire to treat trees like people. People who work with trees have borrowed too much from the people who work with animals. Indeed, trees are different.  The wound dressings and healing rationale fit for animals, but not for trees.
Further reading:
London planetree walls off decay

via the US Forest Service publications website:
Tree Decay, An Expanded Concept
Forest Insect & Disease Leaflet - Oak wilt
How to Save Dutch Elm Diseased Trees by Pruning

2 comments:

  1. Oh neat. I had read a little on the practice in 2008 when I ran into some cement filled Weeping Mulberries trees at The Greenbrier in West Virginia (http://tgaw.wordpress.com/2008/10/14/cavity-filling/), but I don't believe I read these passages.

    I am particularly fond of the quote, "People who work with trees have borrowed too much from the people who work with animals. Indeed, trees are different."

    Thanks for posting and teaching me more about Cavity Filling! : )

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  2. I have seen some fine examples of masonry in the process of cavity filling, usually these works outlive the tree they are trying to save.

    There is another practice that I am not sure is regional or what, but when I was very young I remember seeing lots properties where all the large shade trees were painted white from the ground up to 7 or 8' tall. Perhaps it was decorative, or do you know a reason anyone would do this as a horticulture practice?

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