Poplars are fast-growing trees often used for shade or tall screens between properties. There are different kinds of trees in the poplar family, including aspen trees, cottonwoods, tulip trees and sycamores. What all poplar trees have in common is a faster-than-average growth habit, shallow root system and weak wood that is prone to insect, disease and storm damage. Many people plant poplars they saw advertised as a fast-growing shade trees and then regret the decision after a few years when the common drawbacks of planting poplars begin to appear. That is when the decision is made to kill or eliminate the tree or trees.
Kill the polplar by girdling it. Make a cut with a chainsaw about 2 to 3 inches into the trunk under the bark layer, all the way around the trunk. Don't cut any deeper than is necessary cut into the area where nutrients and moisture are taken up by the tree from the root system, which is the area just under the bark layer. It's best to do this during the heat of the summer, when the tree will begin to decline within a few days.
Spray any sprouts or suckers that come up around the landscape from the root system of the tree, using a weedkiller containing glyphosate. You may need to do several applications to kill all the sprouts.
Cut the polar down, as close as possible to the ground, once it is dead. It will only take a few weeks for the tree to die if you did the girdling correctly. If the tree is still alive, repeat the girdling procedure, but be careful not to cut so far into poplar it becomes weakened and falls over in high wind.
Drill several holes, between 4 and 6 inches deep into the stump, and fill with . You can buy crystallized ammonium sulfate at garden centers. Then, add a little water into the hole to activate the crystals and plug the ends of the hole with softened paraffin wax. This will accelerate the decay process that naturally occurs, and the overdose of nitrogen will kill any remaining parts of the tree.
Or, use a stump grinder to reduce the stump to sawdust. Whatever method you use to remove the stump, you will need to continue to apply glyphosate to the sprouts around the old root base of the poplar until they are eliminated.