In Defense of the Gumball Tree

Sweetgum fruit. Photo credit: Rob Frank

I don’t want to come off as self-righteous, but I feel that I need to step up in this month’s article to defend a native tree that has been falsely maligned and impugned by many folks during my entire tenure at the Alliance for the Chesapeake and for the duration of this Forests for the Bay newsletter. I am, of course, standing up for the sweetgum, Liquidambar styraciflua.

Sure, I get it. Those spiky gumball-like seeds can look daunting, like a thousand medieval chain maces ready to strike those who wander too near, and sure, stepping on an immature gumball can’t feel very pleasant for those that insist on frolicking all around their yards in bare feet. I understand, they can be messy and difficult to rake for those maintaining a well groomed lawn. I’ll admit too, I have been frustrated trying to split sweetgum logs only to be thwarted by their twisted wood grains and then demoralized when these logs rot at a much faster rate than other species on the firewood pile. Ok, they can be a bit in your face in certain areas: sweetgum is known to regenerate like a weed and often reclaim entire fallow agricultural fields creating a monoculture and reducing biodiversity. Up to this point, I seem to be making the case against this tree. So what is there to admire about the sweetgum to push back against its detractors? Sit back and put your shoes back on (if applicable) and let me regale you with the attributes sweet gum bestows upon society.

Sweetgum is the only species in the western hemisphere from the genus of Liquidambar – golly, what a name! It just rolls off your tongue with the reverence already included, doesn’t it? I feel like I should be paying my bills with Liquidambar. All of my investments are in Liquidambar these days, it is a sure thing that never depreciates.

Liquidambar actually refers to the amber color resin that the tree exudes in response to injury. This resin is referred to as storax and has been sold commercially as American styrax (not to be confused with the benzoin resin derived from various species of shrubs and trees in the Styrax genus, which is found mostly in Asia). Sweetgum resin has a pleasant odor and is used commercially for flavors, fragrances, and in pharmaceuticals. It was once used as a form of chewing gum and used medicinally. Liquidambar styraciflua (translated to “amber resin”) is an apt name for this tree. In fact these aromatic resins are also found in the leaves. Next time you see a sweetgum, pluck a leaf, crush it in your fingers, smell and enjoy.

Looking up at a sweetgum tree. Photo credit: Rebecca Lauver

Sweetgum is a very common tree in south central, south eastern forests in the US and has a southern range extending all the way down to Central America. It is most often found in bottomlands, flood plains and riparian areas but can tolerate a variety of deep unconsolidated soil types. Its northern range historically extends to the Mason Dixon Line in the Chesapeake watershed. Although not a common component in forests in Pennsylvania and New York in the Chesapeake region, its ability to tolerate bottomland & floodplain soils has made it a popular tree to plant in urban and suburban areas (which marked the beginning of ‘the troubles’ with those unshod frollickers). Sweetgum is a standard tree in our (the Alliance’s) riparian and upland reforestation efforts throughout the region. It is a hearty tree that establishes well on a variety of sites. We just know it’ll succeed where we need it to.

Sweetgum is a medium to large canopy tree and can grow to over 100 feet in our forests. It maintains an excurrent growth form, which means the central leader (stem) exerts apical dominance (hormonal control) on lateral branch growth. Sweetgum is able to maintain a straight mainstem up through its crown that gives it an oblong or pyramid appearance. This long straight central stem and abundance makes it a popular tree for lumber in the southern states. The heartwood (inner wood) of sweetgum is a beautiful reddish brown and contrasts dramatically from the light tannish sapwood (outer wood). As mentioned the wood is not very rot resistant, so it is typically used for interior products like veneer, cabinets, doors, trim and other mill work.

Sweetgum leaves. Photo credit: Yale University

Sweetgum has distinctive, easily recognizable star shaped leaves that are situated alternatively on branches. It can sometimes be confused with maple species. Maple leaves are oppositely arranged on the stems and, as mentioned, sweetgum leaves have a fragrant odor when crushed. Probably my favorite attribute of this tree, and one that should carry it above the slings and arrows of all of its detractors, is its autumn color. As chlorophyll breaks down in the autumn, sweet gum leaves reveal various shades of purples, reds and yellows. It is quite brilliant like the flames of a campfire (only purple-er).

The bark of the sweetgum is very distinctive too. Young twigs often have unique and random corky wings, Bark of the maturing stem tends to be light brown to light gray with deep, rounded, and sometimes scaly ridges

Sweetgum trees are monoecious, which means male and female reproductive structures (in flowers) are both on individual trees, and have unisexual flowers (separate male and female). These greenish flowers bloom in early spring, and the male flowers, which are oblong, can be seen strewn about the forest floor in late spring. The female flowers, which are more spherical, remain on the tree throughout the growing season as those controversial spiky gumball fruits form. The fruits develop throughout the summer and, at first, are hard and greenish with about 40-60 hard spikes. Just behind the spikes the seeds develop in pairs. As the fruit matures in the autumn, they turn brown and holes develop releasing the small winged seeds that are dispersed by the wind. The husk of the fruit may persist on the tree from autumn through winter. The seeds are a valuable food source for a variety of birds like eastern goldfinches, purple finches, sparrows, mourning doves, northern bobwhites and wild turkeys. Small mammals like chipmunks, red and gray squirrels also consume both the fruits and seeds.

Autumn sweetgum leaves. Photo credit: Yale University

I think we can agree that sweetgum has attributes that we can all love or at least respect. As fall approaches and we head out to the woods to witness the vibrant colors of maples, birches, oaks and cherries, let us not forget to tip our hat to the misunderstood, rarely celebrated sweetgum tree, Liquidambar styraciflua, in all of its autumnal brilliance.