Dead or dying ash trees are not only unattractive, they're dangerous. Storm-damaged or diseased ash trees may be twisted, cracked or otherwise deformed, making them incredibly unpredictable and difficult to fell. Tree borers, insects that get under the bark, feed on ash trees and cause extensive damage to the wood. Borers can move quickly from one ash tree to another. Sometimes, properly felling the trees is the only solution to an infestation or damaged tree problem.
Use a plumb line (or plumb bob) to determine the natural lean of the ash tree. Stand 25 to 50 feet away from the tree and hold up the plumb line, letting it fall naturally to the ground. Line this up with the tree and compare. When you view the tree against the straight plumb line, you should be able to determine which way if any the ash tree leans. Do this visual check at two locations around the tree. If you observe no lean, simply choose which way you want the tree to fall. The side of the tree that points toward your fall path will be where you place your final cut into the trunk.
Don the proper safety gear. Before operating a chain saw or swinging an axe, protect yourself. When you're felling an ash tree, wear work boots, a hard hat, gloves and safety glasses.
Cut a triangular wedge into the leaning side of the tree. Use an axe or chain saw to create a slice in the trunk at a 45-degree, downward-sloping angle. Place the cut several feet from the ground, near your waist level. Slightly below the first cut, make a second slice to meet the bottom edge of the top slice, forming a triangle. Both cuts should bite approximately one-third of the way into the trunk. The ash tree should fall in the opposite direction of these cuts, though extensively damaged trees may not fall straight. If any area of the trunk is damaged by ash tree borers, place your cuts under the infested portion of the tree.
Create the third cut. The third cut is perhaps the most crucial, and it's certainly the easiest to get wrong, so work slowly and with great care. This horizontal cut will go on the opposite side of the ash tree trunk from the triangular wedge, approximately 2 inches above the triangle. The cut will be shallow, penetrating only one-eighth of the way into the trunk. Be sure the cut does not intersect with the first two cuts you made.
Move! Once you make the back cut, you're committing to felling the ash tree. The moment the tree begins to move, get well out of the way. If the cuts are correct and the tree falls properly, it will come straight toward you. Wait a few moments for the debris to settle after the tree falls, and keep all your protective gear in place as it goes down. Wood chips, limbs and other objects can be hazardous when flying through the air, so keep onlookers well removed from the danger zone.
Dispose of all limbs and branches. If the tree is suffering from an ash borer problem, get rid of the wood as soon as possible. The insects will stay in felled wood and potentially will find other trees in your yard on which to feed. To that end, have the stump removed as quickly as possible or treat the remaining wood with insecticides to kill the ash tree borers inside.
If the ash tree you want to fell could potentially damage buildings or other property by falling the wrong way, consider consulting an expert. Clear a path leading away from the tree before you fell it, so you have an unimpeded route of escape.
Check for hazards in the air as well as on the ground before felling any tree. Power lines, other trees and sloping land can pose obstacles to safe removal of the tree.