The sweet gum tree (Liquidambar styraciflua), also referred to as liquidambar, has star-shaped leaves that provide cool shade in the summer then burst into a flush of golds and reds in autumn. This tree, that rises in U.S. Department of Agriculture plant hardiness zones 5 to 10, requires little or no pruning during its life cycle, but you might have to prune it to repair damage in a wind storm, eliminate diseased branches or shape it up. If you do that depends on what you would like to accomplish, but generally the best time to prune is in late winter when the tree is still inactive and disease organisms are inactive.
Pruning After Planting
At the time of planting, you should only prune liquidambar to get rid of damaged twigs. These branches should be pruned back to the back. As the young tree grows over the next three to four decades, prune it into the desired shape through light pruning in late winter. Mainly, you will want to make sure it’s only one major trunk, so prune away any branches close to the top of the tree to leave a single, straight leader branch to your back.
Pruning as the Tree Ages
As the tree ages to four decades and past, prune off root suckers during the growing season every year. In late winter, cut away branches at the top of the major back competing with the leader division. Prune these branches all of the way back to the main trunk. This is also the time to prune lower branches back to the back so you have room to walk beneath the tree. The smallest division of a liquidambar tree in the yard should be 8 feet in the ground, and to get a tree that may eventually hang over a street, it should be 8 to 10 feet in the ground.
Should you prune liquidambar properly in the early stages of its growth, the only pruning you will need to do to your adult tree is to eliminate storm damaged branches, diseased locations or root suckers. If diseased branches can’t be treated successfully, remove them right away regardless of what time of year. If branches have been broken by a storm and threaten to damage nearby buildings, then remove them at once also; otherwise, wait until late winter when the tree is dormant to prune them. This reduces the risk of exposing the tree to infection, especially in the autumn when fungi are prevalent. Remove a division by cutting it back to the upcoming major division, to a grass on the side of the division or to the back.
Sterilizing loppers, pruning shears and chainsaws before working in your liquidambar reduces the danger of spreading infection. Sanitize the equipment from dipping cutting surfaces, and grips subjected to contamination, in 70 percent isopropyl alcohol or wiping it on with a clean cloth. Sanitize chainsaws by removing the chain and letting it soak as you wipe the bar and other surfaces. Alcohol is flammable, so don’t use sterilized tools about open flames. If you’re working on a diseased tree, then spray on the cutting layer after every cut with a household disinfectant.