Botany Blueprint: The Sweetgum

Specimen #6: American sweetgum, Liquidambar styraciflua

appy October, everyone. ‘Tis the season of shape shifting, technicolor costumes, sweet treats, and fearsome accessories. Thus it’s also the perfect time to consider a tree with an according autumn transformation: the American sweetgum (Liquidambar styraciflua). To the sweetgum, the magic of fall is marked by the disappearance of green chlorophyll, a coat of armor for its drying seed case, and a dispersal of seeds. This all provides golden vistas for busloads of New England leaf-peepers, sharp cries from bare-footed naturalists, and low-hanging material for craft projects (a basket of dried sweetgum balls and a can of gold spray paint can be recommended for a constellation of proxy stars on December’s holiday tree).

For most of the year, the tree is fairly innocuous. Native to North America, its dark green leaves and relatively high canopy (20-35m) confer a popular ubiquity — perhaps you’d notice its shade before bothering to identify the sweetgum. However commonplace, the sweetgum is also unmistakable. If asked to draw a “tree,” you’d probably wind up with a sketch of the American sweetgum. If you’ve collected elementary school leaf specimens, it’s likely they were the broad, star-shaped leaves of the sweetgum. And if you’ve emerged from a walk in the woods with a sticky residue on your hands, that could also be from the sweetgum (aptly named “Liquidambar” its amber-colored resin smells like ambergris, and has been used to sweeten the breath and air). These attributes, however, are not entirely unique. The sweetgum’s leaves are often mistaken for a maple, others provide shade just as well, and it’s not the only tree with viscous excretions.

But come autumn, the sweetgum demands particular attention. As the leaves change and prepare to fall, the tree’s pliable, chartreuse fruits prepare to disseminate their seeds. The seed cases harden and become a dark brown. Autumn’s desiccation begins to sharply define their form, and to slowly pry open each capsule. The result is a collection of spiked balls, sweetly animated in dangling rows. The length at which each hangs from the branch affords a dramatic element — pivoting as a seasonal pendulum, swinging like bauble earrings. As they sway, the balls release their seeds to the wind. Each woody seed case is built with about fifty distinct capsules, all fused at an interior point. The sharp mouths almost resemble a chorus from the Greek Underworld, or a brood of infant birds. Perhaps appropriate with the metaphor, each orifice yields a litter of material, but only one to two viable seeds. Delicately winged, these seeds land some sixty meters from the parent tree. The remaining matter is misshapen and dense — each an aborted seed.

When the fifty mouths have emptied, the tree releases the seed case itself. Accumulating like an artillery of medieval weapons, the sweetgum’s cast-offs are generally noticed not by tree-gazers, but by those who do not tread lightly on the sharp carpet. The tree’s detractors moan that the balls are painful to the flesh, and a nuisance to clean up. As such, the sweetgum is also known as “ankle-twister” (in addition to its perhaps gentler nicknames: “space bug”, “monkey ball”, “bommyknocker”, “bir ball”, “gumball”, “conkleberry”, “cukoo-bir”, and “porcupine eggs”).

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