Black walnut is an expensive and much-desired wood, but the tree is non-native in large areas of North America and classified as invasive in others. Black walnut trees are best used only in large landscapes where the juglone produced by their roots (which is toxic to some plants) can be offset by their placement, proper composting and prudent choice of plants placed in proximity to them. If, however, the tree becomes invasive or the day comes when it must be removed, salvage as much as possible and kill the remains completely.
Fell the Tree
Plan which way the tree should fall and measure to make sure you have enough room. Locate safe paths back and away from the direction of fall when the tree comes down. Suit up in hard boots or steel-toed shoes and close-fitting, long-sleeved shirt and slacks. Borrow a hard hat with a visor or rent it along with a chain saw or power chipper.
Remove top and outer branches with loppers, pruning saw or chain saw, depending on their size. Work back to the main trunk or “leader” of the tree. Remove large branches in sections so falling sections don’t damage underlying turf.
Take the main tree down a section at a time, using double cuts. First cut a “V” horizontally across the trunk on the side of the direction in which you want the section to fall, then cut around the trunk on the opposite side above the “V”. When the tree starts falling, walk away from it at a 45-degree angle to the line of fall behind the tree’s movement.
After the tree is down, cut the trunk off as close to the ground as is safe to do.
Complete the Kill
Apply an herbicide that contains 20 percent glyphosate to the stump of a felled tree with a sprayer. Wear a mask and gloves when handling herbicides and follow the directions on the label. Glyphosate herbicides are commonly available to consumers but, according to the Invasive Plants Association of Wisconsin (IPAW), triclopyr may be more effective in killing black walnut.
Cut shoots that appear around the stump with hand pruners or loppers as soon as they appear. Black walnut roots are very strong and may put up shoots for years after the tree has been taken down.
Spray around the bark on the lower part of sapling with Garlon 4, a hydrophobic triclopyr herbicide. According to IPAW, the solution will sink into the bark, travel to the roots of the plant and kill it completely.