My tree is hollow inside — what should I do?

An open cavity you can see or reach into, usually at an old branch stub, a storm wound, or the base; a stretch of trunk that thuds dully when rapped, compared against sound trunk higher up on the same tree; a squirrel or raccoon living in the stem, or ant traffic in and out of a hole; piles of sawdust-like frass below an opening; bark that sounds papery and sits over nothing behind it. Hollow is not automatically dangerous, and this is where homeowners get oversold more than anywhere else on this list. A tree is a tube, and a tube carries bending load in its outer wall — a hollow stem with a thick continuous shell can be as strong as a solid one. What actually matters is the thickness of remaining sound wall relative to trunk radius, and whether the cavity is closed or has an open slot in the side. An open slot is worse than a sealed hollow of the same size because the tube can no longer resist flattening inward. Neither of those is visible by looking at the hole.