There are mushrooms growing at the bottom of my tree — what should I do?

Clusters of honey-colored mushrooms in the lawn ring around the trunk in fall; a hard shelf-like bracket fused to the trunk flare, often brown on top and white underneath and bruising when scratched; a black or white crust in the bark seams right at ground level; a flare that looks sunk or column-like going into the ground instead of spreading out; a dull thud instead of a sharp crack when you rap the base with a hammer handle. The crown may look completely fine — thinning is a late sign here, not an early one. A fruiting body is the reproductive organ of a fungus that has already been eating the inside of the tree for years. By the time anything shows on the outside, decay is established in the root plate or the butt of the stem — the exact structural zone that holds the tree upright. This is the one common finding where an outwardly healthy tree can come over whole, roots and all, in an ordinary thunderstorm. It is an anchorage question, not a branch question.