Cavity Filling

October 14, 2008 at 8:00 am 9 comments

When we were at The Greenbrier, we did stumble upon something interesting. A lot of their Weeping Mulberry trees had their holes filled in with cement.

A Weeping Mulberry… filled with cement

This perked my curiosity enough to do some Internet research when I returned home. It turns out this is a practice called “Cavity Filling”. It was invented by a tree surgeon named John Davey. The idea was to fill in hollow trees or crevices with cement to stabilize the tree and give it a chance to grow around the filling and heal itself. In 1901, the practice made multiple appearances in Davey’s book, The Tree Doctor.

(Photo from John Davey’s The Tree Doctor, published in 1901)

Modern research has indicated that all trees do not in fact heal when properly filled. Here’s an excerpt from Greensboro, North Carolina’s “Tree Myths” page:

Filling of hollow trees, a process called “cavity filling,” was practiced by arborists for many years. Thanks to modern research, it has been discovered that cavity filling is not needed to support or improve the health of hollow trees.

Tree experts have found that cavity filling with cement can actually damage a hollow tree. According to Bob Rouse, Staff Arborist at the National Arborist Association, “The column of cement created in the tree by a cavity fill doesn’t move, just like a column on a building, but the tree is always moving. It sways with the wind constantly. The rubbing created by the swaying tree and the solid column of cement further damages the tree.

Decay organisms, such as rot fungi, that created the hollow in the first place are able to take advantage of the new injuries created by the rubbing and invade the healthy tissue of the tree. Rouse adds, “If that wasn’t bad enough, the cement holds moisture, creating a favorable environment in the filled cavity for the decay organisms!”

Research contradicting conclusions from the past didn’t strike me as odd– that happens every day. What did surprise me about cavity filling was that it had been a common practice by arborists for over 100 years. In recent times, I’ve paid quite a bit of attention to trees. How have I not seen this before?!?

And then I remembered… The hollow trees and the trees riddled with deep crevices I run across are typically in the woods!  Looking at them, Bob Rouse from the National Arborist Association may be correct. These trees don’t have the luxury of cement and they are managing to get along.

Bottom Creek Gorge – Duvall Trail

Appalachian Trail – Guillotine Rock

Andy Layne Trail – Tinker Cliffs

Appalachian Trail – Brush Mountain

Appalachian Trail – Petite’s Gap

Appalachian Trail – Kelly’s Knob

Entry filed under: Appalachian Trail, Hiking, Travel, trees, West Virginia.

Rhodos All Around links for 2008-10-14

9 Comments Add your own

  • 1. geekhiker  |  October 14, 2008 at 2:16 pm

    Ah, yes, the “cement solution”. Reminds me of an old neighbor who used to posit that the best backyard wasn’t a lawn, but a large expanse of flat cement.

    I’m not surprised by the findings, particularly given the size of some of the gaps in old redwoods I’ve seen!

  • 2. Aaron  |  October 16, 2008 at 7:58 pm

    I need a local tree-hugger to figure out what kinda funk I got growing on one of my trees. For the life of me, I can’t figure out if it’s a fungus or bugs in the bark or what!

  • 3. Kelly’s Knob Tree - Not Dead « TGAW  |  October 24, 2008 at 8:01 am

    […] 24, 2008 One of the trees I highlighted in the Cavity Filling post was a tree right at the top of Kelly’s Knob. That tree is so hollow and so riddled with holes […]

  • 4. Los Gatos Dentist  |  February 7, 2010 at 11:46 pm

    That is one heck of an old tree!

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  • 8. wish_I_knew_more  |  November 20, 2011 at 10:46 am

    I know they say filling the tree with concrete can accumulates water and many will talk about the fact that concrete won’t flex. … and I think they say they’ve seen damage from it. Still, I have to wonder if there isn’t some value to the concrete in some situations. We do see very old trees that have been patched with concrete long ago. As an architect, I have to appreciate the structural strength of a filled pipe. It would seem to me that there are some cases when maintaining the inner integrity of the core would sustain strength that would be lost otherwise. Compartmentalized or not, a thin walled tube will crush when heavily loaded under bending.

    I’m not an expert but I wish the research were better oriented around the circumstances and design-characteristics of the repair. There are some trees that seem to last decades with these repairs. But then again, we probably do not see many of the ones that do not.

  • 9. Voice of Reason  |  July 27, 2012 at 4:13 pm

    the whole reason arborists are against filling trees with concrete, is it makes them harder to remove. Well they should be more difficult to remove, they are sturdier. The only issue I can see is, the tree may flex at the top of the concrete column instead, and eventually crack or break there.


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