Cottonwoods are short-lived, but can grow to more than 100 feet before they need to be brought down. Fell cottonwoods in autumn, when leaves are gone and you can see the tree's structure clearly. Choose a day with calm winds for cutting down a tall specimen, because strong wind may influence the direction of its fall. A cottonwood with a diameter smaller than 6 inches may be felled with a single cut and guided by hand. If the tree is larger, some forethought will be required.
Plan which way you want the cottonwood to fall. Note where the tree stands in relation to cars, buildings, streets and power lines.
Put on safety glasses, hard hat and gloves. Clear brush and undergrowth in the immediate area of the tree. Create at least two obstacle-free paths away from the tree for safety purposes. Practice using these routes until you can get away from the tree fast.
Start the chain saw. Set the blade at a 45-degree angle on the side of the cottonwood facing the direction it will fall, about 2 feet from the ground. For instance, if you want the tree to fall to the west, make the cut on the west side of the tree. Cut downward at 45 degrees toward the center of the trunk. Make a second, horizontal cut 8 to 10 inches lower meeting the end of the first cut and creating a V-shaped notch.
Go to the other side of the cottonwood. Make a third, horizontal cut 1 inch above the notch. Do not cut all the way through. As the chain saw blade gets near the notch point, the tree will begin to fall in the direction of the notch.
Turn off the chain saw and get away from the tree, using one of your clear escape routes. Move in when the tree stops rocking. Cut large limbs from the trunk first, then cut the trunk into sections for firewood. Cut small limbs with pruning shears for use as kindling or compost.
Turn on the chain saw one last time and cut the cottonwood stump as close to ground level as possible.