At my high school reunion this summer (a milestone year, not saying which one) someone asked, “Is there anything to get rid of sweetgum balls?” Here’s the answer I promised my classmate.
The American sweetgum is named for the sweet, sticky sap that comes out of any wounds in the tree. The genus name, Liquidambar, means liquid amber, just as it sounds. One of the earliest written accounts of sweetgum is from 1519, when one of the conquistadors wrote about seeing Montezuma smoking a reed filled with tobacco flavored with sweetgum sap.
The sap has been used for centuries in assorted herbal remedies, cosmetics, and make-shift chewing gum. The hardwood lumber is too brittle for some uses, but is often made into plywood. In recent years, sweetgum trees have become a source of shikimic acid, from which the medicine Tamiflu is derived.
The medium-to-large trees are moderately fast growing and provide excellent shade in the summer. The fall color is beautiful with the star-shaped leaves turning shades of yellow, red, and burgundy all on the same tree. Those leaves don’t fall off until almost winter, prolonging their fiery display.
Then you look up and see the bare limbs with spiky balls hanging on them. Later the sticker balls start to fall, not all at once, but slowly for weeks and weeks through the winter into spring. Each beak-like spike held two seeds that the birds and squirrels have already enjoyed, so the balls are dry and empty by the time they fall.
Some crafters create attractive displays using sweetgum balls, spray paint, and hot glue. Children who have heard stories about snowball fights can substitute sweetgum balls during our warm winters. Sweetgum balls as mulch might help keep slugs and other pests away from your plants. Most gardeners consider the balls a nuisance. Michael Dirr, in his Manual of “Woody Landscape Plants” complains, “I have slipped, fallen, and taken offense.”
One solution is to plant fruitless varieties. The best known is ‘Rotundiloba.’ The lobes of the leaves are rounded (rotund). You might miss the pretty star shape of the traditional sweetgum leaves, but the fall color is still attractive.
For established trees there are two methods sometimes dubbed “birth control for trees.” One is a spray called ethepon, and the other (brand name Snipper) is an injection at intervals around the trunk of the tree. Both are plant hormones applied when the tree starts to flower, making the flowers fall off before they set fruit. Sweetgum trees have separate male and female flowers, and neither is showy. A professional arborist can identify them and time the application.
It’s difficult for an amateur to spray a large tree thoroughly without getting drenched with chemical and scattering spray on other plants. Snipper appears easier to apply and can be ordered online for about $150, but the company makes no guarantees because timing is so critical. Both treatments are good for only one growing season, so it’s a yearly expense if you choose to eliminate sweetgum balls.