Sweet Gums (Liquidambar styraciflua) are among the commonest trees in the South, and are found in huge numbers throughout the Piedmont and Coastal Plain of North Carolina. Although the spring flowers are fairly large, they are held high in the tree and are difficult to see. An occasional low-hanging branch reveals an active cluster of early leaves and specialized flowers. Sweet Gums are monecious (having both male and female flowers), but unlike Elms, both sexes are not found within a single flower – each sex has its own separate flower. In the photo below, the leaves of the Sweet Gum are unfurling while the male flowers (staminate flowers) are clustered above the leaves and the female flowers (pistillate flowers) are suspended below the leaves.
A closer look at the male flowers shows large numbers of very small flowers gathered in clusters on a thick stalk above the branch. Sweet Gums are wind pollinated, and these flowers produce huge quantities of pollen. Fortunately the pollen is only mildly allergenic and not a major cause of spring hypersensitivities.
While most people will never see the colorful male flowers on the tree, they certainly see them underfoot, on sidewalks, patios, decks, driveways, and lawns, where they appear by the thousands, perhaps by the millions, every spring.
The female flowers remain on the tree, suspended as a single, spherical structure with masses of tiny flowers. The curled, tubular structures covering the surface are the stigmas of the flower, whose surface is sticky to catch the pollen.
During the summer , this soft and delicate structure is transformed into a hard, prickly, and complex fruit made up of seed capsules. The “gum balls” are highly unpopular with homeowners trying to maintain their lawns and keep their sidewalks clear. They are tough on bare feet and gather in such numbers as to make walking unstable.
There is a seedless, sterile cultivar called “Rotundiloba”, that has been grown and propagated (vegetatively of course) for commercial sale. Its leaf lobes are rounded rather than pointed, giving it an odd, unnaturally smooth look to many eyes. Interestingly, the original tree was a native found in North Carolina in the 1920s.