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Visiting a park in Portland, I saw a huge old oak with a massive cavity filled with expanding foam.
Some crew clearly tried to 'save' it, but I've heard that can trap moisture and rot it from the inside. What's the verdict on cavity fills these days?
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val_wilson5mo ago
Hot take: Usually makes it worse.
Oh man, that's the old school way to do it and it's pretty much a disaster. It seals all the moisture in like a plastic bag, so the wood just rots out behind the foam. These days, the best practice is often to just leave the cavity open, maybe put in a drain at the bottom, and let the tree compartmentalize the damage itself. Filling it mostly just helps the people who see it feel better, not the tree.
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the_nina5mo ago
Honest question, does it really matter that much for a tree in someone's backyard? Like, sure, if it's a big old oak on a busy street, maybe. But most of these cavities are small and the tree just deals with it. I've seen trees with big gaping holes that have been fine for decades. Feels like arborists get a little overprotective sometimes, don't you think?
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