In nature trees pretty much look after themselves, but if you have one in your yard it’s going to do a lot better if you give it some care and attention. The fact is that, in the wild, trees have a pretty high attrition rate. For every stately tree whose shade you relax under in the woods, dozens never made it past a few feet high and hundreds more perished as seedlings. Even once a wild tree reaches maturity it faces a lot of threats. Pests and disease kill many, and others fall victim to their own success.
Walking through the woods you’ll see a lot of dead branches, both on the ground and still on the tree. Many things can kill a branch, from storm damage to fungi, and once a limb has died it presents a menace to both anyone walking underneath and to the tree itself. Deadfalls can cause serious injuries if one happens to land on you, while the extra weight leaves the tree more vulnerable every time the wind gets up. In nature this is all part of the complex system that maintains a healthy balance, but it isn’t something you want in your yard. Every year thousands of homes are damaged, and many people are injured, when a branch falls or a whole tree is brought down by the weight of dead or unbalanced limbs. In almost every case the main cause was failure to trim it properly.