The Liquidambar styraciflua, also known as liquid amber or sweet gum tree, is commonly planted in locations where the homeowner is seeking quick shade and attractive fall colour. Liquid amber grows to 100 feet. Unfortunately, the rapid growth is offset by the spiny seed balls, shallow root system and easily damaged limbs. In addition, after the tree is cut down, the remaining roots may sprout into new trees. Killing a liquid amber tree is not always easy, but a determined homeowner can do it.
Call a tree service. Removing a tree that is up to 100 feet tall is a job for professionals. The tree service will obtain the city permit, cut down the tree, remove the wood and grind the stump. The service generally cannot remove or grind every tree root, however, and liquid amber trees are known for sprouting, or suckering, from the remaining root system.
Cut the bottom out of a coffee can and place the can over the sucker. Spray an herbicide containing glyphosate--Roundup, for example--into the can and onto the leaves of the actively growing suckers. The coffee can helps prevent over-spray.
Alternatively, paint the herbicide onto the leaves of the suckers, using a paintbrush. Use this method if the suckers are growing up among your prize roses or other shrubbery.
Scrape the bark down to the inner green stem of the suckers, if you don't want to use an herbicide. Pour equal parts of rubbing alcohol and water into a small spray bottle and spray the exposed green skin of the sucker, soaking it thoroughly. Repeat as necessary until the sucker dies.
Mow over suckers in the lawn as soon as they appear. Do not allow them to become established.
Persistence is key in killing a liquid amber tree. Check every weekend for new suckers.
Wear gloves and safety glasses when spraying herbicides or rubbing alcohol. Use caution with products containing glyphosate if there are other trees in the area. The herbicide can travel through the intertwined root systems and kill desirable trees. Do not spray herbicides on a windy day, even using the coffee can method. Over-spray is likely to kill everything it touches. If you accidentally spray the wrong plant, wash it down with water immediately.