Paulownia tomentosa, commonly called the princess tree, royal paulownia and empress tree, has a growth habit that makes it a pest to many gardeners. The princess tree originates in Asia and is hardy in U.S. Department of Agriculture plant hardiness zones 5 through 8. The tree produces pecan-shaped fruits that upon bursting release thousands of seeds. The seeds germinate readily almost anywhere they land, including roadsides and riverbanks. Manual removal of princess trees works if you manage to destroy all of the roots, but an herbicide application is the most reliable way to kill the trees.
Manual Removal Methods
Pull princess tree seedlings by hand as soon as you notice them. When pulling, remove each seedling's entire root system to ensure the plant doesn't sprout again. The removal process is easier when the soil is soft after a rain.
Chop down each young princess tree at the base of its trunk before the tree begins flowering and producing seeds. Use a manual saw or power saw for the task. This method is only a temporary solution because each tree will continue to sprout. Applying an herbicide is necessary to remove each tree permanently.
Wound the trunk of each princess tree that is too large to remove by hand or chop down. Use a hand ax to make a circular cut around the entire trunk about 6 inches above ground. Applying a foliar herbicide, such as one containing glyphosate or triclopyr, may be necessary to kill the tree.
Herbicidal Removal Methods
Spray each princess tree's trunk, branches and leaves with a foliar herbicide if you're not concerned about damaging other plants in the area. Fill a hand sprayer with a 2 percent solution of glyphosate or triclopyr and water, and add a 0.5 percent non-ionic surfactant. Set the hand sprayer to its coarse spray pattern, and use low pressure when applying the herbicide. Glyphosate kills any plant it touches, but triclopyr affects only broadleaf species it contacts.
Make cuts with a hand ax into each princess tree's trunk every 3 inches and about 6 inches off the ground. Apply a solution of 50 percent glyphosate or triclopyr and water to each cut immediately after wounding a tree. This method works well for large trees.
Coat each tree's trunk with a solution of 25 percent triclopyr and 75 percent horticultural oil. Start applying the mixture at the base of each tree's trunk, and work your way up the trunk to a height of 12 to 15 inches. Wet each trunk thoroughly until you see runoff at the ground line. This method works only when the ground is not frozen.