Mushrooms or conks at the base. Fungal fruiting bodies on the root flare or lower trunk mean decay is already well established inside the wood — by the time the mushroom appears, the fungus has been eating the structural core for years. A tree can hold a surprising amount of rot and still look healthy in the canopy, right up until the day it doesn't.
A crack or seam running vertically up the trunk, especially where two main stems join. Co-dominant stems with included bark between them are the single most common failure point we see on water oaks and Bradford pears across Gwinnett and Walton. That V-shaped union is not a crotch, it is a seam waiting for a wind load.
Fresh lean with soil heaving on the opposite side. A tree that has leaned for forty years and grown reaction wood to match is usually fine. A tree that leaned last month, with a ridge of lifted soil or exposed roots on the high side, is a tree with a failing root plate. That one is urgent.
Deadwood in the upper canopy that keeps coming back. A few dead twigs in the interior is normal shading. Large dead limbs at the top, year after year, usually means root damage, girdling, or decline the tree cannot grow out of.
Construction within the drip line in the last five years. Trenching for a driveway, a pool, or a utility run cuts the roots the tree was standing on. The canopy often looks fine for two or three seasons and then collapses all at once.
Finally, watch for carpenter ants or sawdust at the base. Ants do not eat live wood — they move into wood that is already soft, which makes them a symptom rather than a cause, and a reliable one. If you are seeing any of these, a free on-site look costs you nothing and we will tell you honestly if the answer is pruning rather than removal.