Cavity in Elm Tree
Q: How do we fill or repair a cavity in our elm tree?
A: Typically, you do not need to fill a cavity in a tree.
In the old days we probably would have filled the cavity with cement, but it
was discovered that this didn't really help, and actually could cause
By filling the cavity, the tree was made less flexible at that
point, and the top would occasionally snap off above the cement.
Also, as the tree flexed in the wind, if the cement "came loose" inside the
cavity, it would bang against the cavity walls, injuring the tree further,
which helped decay to advance. So, you can see, that wasn't as great of an
idea as it sounded like.
Instead, I would have an arborist check the cavity to see if the structural
integrity of the tree is compromised to the point that the tree should be
removed for safety reasons. If it is determined that the tree can be
retained, leave the cavity alone, although you can pick out any loose bits
of decayed wood that may be in there.
If you really want to fill the cavity for some reason, you can use expanding
foam insulation (like the stuff they use around window and door frames).
However, this is not really necessary, at least from the tree's standpoint.
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