What woody creature lives for hundreds of years, is known for its fall colors, and produces a fragrant substance to protect and care for itself?
The sweet gum tree!
The spiky balls they shed were a staple sight throughout my childhood in New York City, but sweet gum, like many other trees, really caught my eye this past year as quarantine measures grounded me to my neighborhood. I’ve always loved taking long walks through the cities I’ve lived in, and without other places to go, I’d repeat the same routes through the seasons, noticing in much more depth the changes in the plants surrounding me.
I began collecting leaves last autumn, marveling at their artful color combinations, the intricacy of their vein systems and gradients, and the remarkable variety of shapes across species. Perhaps my favorite of all the fallen leaves I collected last year was one star-shaped sweet gum leaf. With what looked like scales of corroded pigment revealing the leaf’s interior, and dramatic contrast reminding me of cosmic explosions, this leaf immediately captivated me. Where did it come from?
The sweet gum is found throughout North America. Its native range extends from Connecticut to Florida in the temperate United States, and in tropical montane regions of Mexico and Central America, but people have spread it far beyond that original area.
Liquidambar styraciflua has many names – it is known as American storax, hazel pine, bilsted, redgum, satin-walnut, star-leaved gum, alligatorwood, and of course, sweet gum.
Many of these are straight to the point, as the tree, which has star-shaped leaves and bumpy, ridged wood, exudes a gummy sap with a sweet fragrance when it is wounded. Its Nahuatl name, Ocotzocuahuitl, translates to ‘tree that gives pine resin’ – from ocotl (‘pine’), tzotl (‘resin’), cuahuitl (‘tree’), again showcasing this key attribute.
According to historical records, Spanish explorers first encountered the sweet gum when coming into contact with Indigenous civilizations in Central America. Don Bernal Diaz del Castillo, a companion of the conquistador Hernan Cortes, referenced ceremonies between Cortes and the Aztec ruler Montezuma that involved partaking of a liquid amber extracted from a sweet gum tree.
Botanically, this resin is exuded by the sweet gum when the tree experiences injury. It seals over any wounds and hardens into a scab. The flow of sticky sap can also deter insects from burrowing into the wood and prevent herbivores from consuming the tree.
A Spiky Exterior
The sweet gum is known for its beautiful foliage, with the pointed star shaped leaves shifting from green to an array of bright colors during autumn months, sporting shades from deep purple to golden yellow. As a result, the trees are often prized for landscaping purposes. However, their leaves are not the sweet gum’s only noteworthy feature.
The trees’ branches feature angular shapes produced by plates of bark attaching edgewise to the branches. These hard ridges of wood come off the branches’ surface at perpendicular angles, creating a scaly look that inspires the commonly used name “alligator wood.” This feature increases the surface area of the trees, and to some appears to be a disadvantage to planting sweet gum, as the branches can accumulate more ice and snow in winter, building up heavy loads.
As mentioned, the sweet gum also produces hard spiky balls to the delight or dismay of schoolkids across the East Coast. I used to enjoy kicking these around, treating them as ubiquitous little toys without bothering to figure out what they were. It turns out that these are actually the fruit of the sweet gum, which contain its many sawdust-like seeds. The spiky pods can be quite difficult to break open, but when the season is right the wind disperses seeds, providing food for many different creatures.
Birds like eastern goldfinches, purple finches, sparrows, mourning doves, northern bobwhites and wild turkeys eat the seeds. The fruits and seeds are also enjoyed by some small mammals such as chipmunks, red squirrels and gray squirrels. Some people find the fruit to be a nuisance and walking hazard, but to the animals that ingest them, the spiky pods are a welcome feature of the ecosystem.
Indeed, sweet gums offer many contributions to their ecosystems. By providing food and habitat, they support a variety of bird species, mammals, and insects, including playing host to the larval form of the lovely luna moth caterpillar.
We humans have found many uses for the tree as well, from the fragrant resin to the hardy wood. The wood from the sweet gum tree is one of the most important commercial hardwoods of the Southeastern US. It is used to build furniture, interior finishing, boxes, crates, and pallets.
The sweet gum tree resin is also used medicinally. Traditionally, Native Americans use infusions of the bark to treat diarrhea and dysentery and to create poultices for cuts, sores, and bruises. Bark infusions can also be used to aid against a number of conditions including asthma, coughing, and digestive problems. Finally, the resin can be made into chewing gum, a natural precursor to the minty products so popular today.
This tree has both beauty and brawn, form and function. The more I’ve learned, the more I’ve come to appreciate the complexity behind the familiar sight of sweet gum. I hope you learned something new too!
By Maya Dutta