Rub your fingers with the leaves of Florida trema, Trema Micrantha, and you’d swear you’re rubbing a sheet of sandpaper. It’s that rough.
In fact it’s distinctively rough. So rough that one can almost identify Florida trema by touch alone. Rougher than just about any other plant that we experienced in the wilds of South Florida.
As the name implies, Florida trema is a Florida native, though no one is quite sure where or how Florida became part of the name — the Sunshine State is the northern-most point where it grows and only a small slice of its overall range. Florida is the only state in the union where it’s found. Within Florida, it grows as far north as Okeechobee County, but it’s rarely found north of Broward County. The U.S. Department of Agriculture’s PLANTS database includes every county from Lake Okeechobee south into the Keys as part of range. The Atlas of Florida Vascular Plants is much more limited, including only Broward, Palm Beach, Martin and Okeechobee counties.
It is also found throughout the Caribbean, Mexico, Central America and South America. More on its range, particularly how it seems to be creeping north, in a bit.
Florida trema is a perennial, a shrub or small tree, maybe approaching 40 feet tall when fully mature. Most of what we’ve seen skews toward shrub, however.
The bark is light to dark brown, relatively smooth, but becoming “warty” as the plant ages. Leaves are long and relatively narrow, the length being about two-and-a-half to three times the width, and come to a sharp point at the apex, or tip. The leaves are simple, arranged alternately and sort of in two ranks, one each side of a branch. They are densely covered with short, stiff hairs, the source of the sandpaper feel.
Florida trema flowers are small, white to yellowish green and produced at the leaf axils, the point where the leaf stem meets the branch. Flowering season is mainly in the spring and summer, but younger plants will bloom throughout the year. The fruit is a small, orange BB-like berry (technically a drupe) that appear on the plant mainly in the fall and winter. Again, like the flowers, younger plants will fruit throughout the year, older plant in the more restricted time frame.
Florida trema prefers full sun, but can tolerate a bit of shade. It can grow in variety of soils, but requires some organic matter in order to flourish and it’s most likely to be found where there’s some limestone, like marl prairies and places where there are outcroppings. Favored habitats include the edges of hammocks and openings in hammocks.
It is a “pioneer” species, meaning it’s among the first plants to take hold in a new clearing created by fire or the downing of a tree, or by us humans, like the side of a road. It grows rapidly, able to approach 10 feet tall within two years.
Florida trema is not cold-tolerant, which is why historically it has been rare north of Broward County. The late Florida Atlantic University Professor Daniel Austin, in his book, Florida Ethnobotany, noted that he had started seeing Florida trema more commonly in South Palm Beach County during the early 2000s. He also noted that cold winters were becoming rare events in the region — the last time it snowed in Palm Beach County was in the late 1970s, and the last frost was in 1989-90.
Putting two and two together, Austin concluded this slow “creeping” northward of Florida trema and other tropical plants was a subtle sign of climate change.
Florida trema is an important plant in the natural scheme of things, providing significant food and shelter for wildlife. It’s a host plant for the io moth and the martial scrub hairstreak butterfly.
For us humans, it has multiple uses. As lumber, it has a bit of a mixed reputation, used to make small things like match sticks. In places it’s used to make boards and rafters, but some say the quality of the wood is dubious. It's also used to make charcoal. The bark is fibrous and is used to make cord.
The sap of Florida trema is used in some traditional medicines to relieve sore eyes. The Seminoles used it to treat women undergoing difficult births and also to treat indigestion.
It is rarely grown commercially; its landscape uses pretty much restricted to restorations and natural settings, according to the Institute for Regional Conservation.
Florida trema has a look-alike cousin commonly called West Indian trema or pain-in-the-back (T lanmarckiamum) with which it’s sometimes confused. West Indian trema, however, has smaller leaves and is found only in southern Miami-Dade and Monroe counties. So if you see trema anywhere north of there, it's likely our guy, Florida trema.
Other common names for Florida trema: nettletree, Jamaican nettletree and capulin. Taxonomic note No. 1: Many sources list Florida trema as a member of Ulmaceae, the elm family. Its leaves do recall those of an elm. However, the federal Integrated Taxonomic Information System considers Cannabaceae, the hemp family, as the accepted classification, and so that’s where we put it.
Taxonomic note No. 2. You will see references to Trema micranthum as the binomial name for our guy. It is an old name and no longer accepted by ITIS. Linguistically the difference between the two? Good question. Micrantha is Greek and means "small anthers," a reference to parts of the flower. As for micranthum, the only meaning we could find is "tiny flower," which seems to add up to the same thing as micrantha. Perhaps someone with actual linguistic or botonical skills can parse the difference.