Here are some signs that your tree may need to be completely removed:
1. Mushrooms are growing near the base of the tree.
2. Areas of rotten wood or cavities.
3. Noticeable change in the leaning of a tree.
4. Excessive leaf loss or dead leaves (see topping below).
Topping:
A tree derives its nutrients from the leaf canopy. When over 50% of the canopy is "topped," the tree will starve and regrowth will usually be spindly and weak. At this point, it's probably going to fail and might as well be removed.
If a dead or dying tree poses an immediate threat to people or property, it could be cheaper to remove it before more costly damage is done.
