Schizaeaceae, the Curly-Grass Fern Family
This is an unusual fern, with vinelike fronds (the leaves of ferns) that can grow to 90 feet long. The rachis is slender, winding and twining. The sterile pinnae (major segments of the leaf blade) are opposite or alternate on the rachis, triangular in shape, bipinnately compound, superficially resembling miniature fronds of bracken fern (Pteridium). The pinnules (divisions of the pinnae) are pinnate or pinnatifid, with a long and slender terminal lobe. The fertile pinnae are borne on the same fronds as the sterile ones, but they are much lacier in appearance due to the slender, fingerlike lobes of the pinnules.
This species is native from eastern and southeastern Asia, through Indonesia to northern Australia, and is occasionally weedy in the tropical parts of this range. It is apparently absent from South America and Africa. In the United States, it has naturalized throughout the southeastern coastal states from North Carolina to Texas, and in Arkansas. It is also reported from Hawaii and Puerto Rico.
The Japanese climbing fern is rapidly expanding its range in Florida. While it is still most common in the Panhandle and the northern peninsula, it has been collected throughout the state. It is most often found in cut-over flatwoods, pine plantations, roadsides and other disturbed sites, but it is becoming a pest in natural areas, where it smothers native vegetation with its rank growth.
The very rare native Hartford fern (Lygodium palmatum) has only been collected once in Florida, and it is doubtful that it still exists in the state. It is distinctive in its palmately lobed pinnae. The very invasive Old World climbing fern (L. microphyllum) is becoming a serious pest in parts of Central and southern Florida. It differs from the L. japonicum in its once-pinnate pinnae and unlobed pinnules.
The plant grows from thin, long-creeping, profusely branching rhizomes, which enable a clump to increase rapidly in size. But the abundantly produced, very light, windborne spores are responsible for long-distance dispersal. Since the plant is common in pine plantations and flatwoods, its spread has been facilitated by the harvesting and removal of pine straw.
Like so many other weeds, the Japanese climbing fern was originally introduced as an ornamental. It escaped cultivation and is now classified as a noxious weed by the states of Florida and Alabama. In most parts of its introduced range in the Southeast, it is killed to the ground by frost in the winter. The dead stems are a hazard because they provide an avenue for fire to reach into the canopies of the host trees.
Langeland, K.A., H.M. Cherry, C.M. McCormick and K.A. Craddock Burks. 2008. Nonnative plants in Florida's natural areas. The University of Florida, IFAS Communications Services, Gainesville, Florida. 193 p.