Aspens are attractive, fine-leaved deciduous trees, found in forests and the home landscape. Aspen trees propagate from seed, but primarily from suckers which they send up at an alarming rate. Removing an aspen tree is not as simple as cutting it down because the trunk will continue to sprout. There are two choices for permanent removal: herbicide or tree girdling. Herbicide is applied to the stump upon tree removal, and girdling is done a year before tree removal. The goal of each is to keep the root system from living and creating baby aspens.
Paint on undiluted glyphosate non-selective herbicide directly to the cut surface of the stump. This should be done as soon as possible after the tree has been cut so the cut has not had time to seal. The glyphosate will enter the phloem and cambium and travel to the roots to kill them.
Drill holes into the stump approximately 8 to 10 inches deep. The number of holes will vary by the size of the stump but there should be at least 12 to 15 holes. Fill the holes with nitrogen fertilizer. Keep the tree moist for the next few weeks as the high nitrogen causes a wood decaying fungus to grow. The fungus will eventually destroy the tree.
Wait for the stump to disintegrate. This will take four to six weeks depending on the size of the stump. You can plant in the location as soon as the bark and wood has rotted away. If you can't wait, pull out the stump with a truck and a chain.
Use the bark blade to shave off the bark all around the trunk at least 6 inches wide. This should be done in May or June when the sap is running. This makes the bark easier to remove.
Use the girdling saw to shave off a layer of cambium and phloem. This interrupts the transmission of sugars in the tree. Do not cut deeply or the xylem will be affected, which signals the tree that it needs to send out more suckers in defense. Every tree in the area needs to be girdled, as they are all probably grown suckers or clones of a central parent tree. It is not sufficient just to girdle the parent tree.
Wait a year for the tree to show signs of ill health. The girdling process is slow as the tree has other food storage. Once it uses up its stores it will begin to decline, because it is not getting extra nutrition from the soil. After a year the tree can be cut down with a chain saw and the stump removed with stump enzymes or the chain/truck method.