Photographer: James H. Miller & Ted Bodner Affiliation: Southern Weed Science Society Source: Bugwood.org Copyright: (CC BY 3.0)
The Japanese climbing fern (Lygodium japonicum) is a vine-like perennial that climb over shrubs, trees or structures. The stems can grow up to 90 feet long and are green, orange or black; and are difficult to break. Leaves are doubly compound and vary in appearance. The overall appearance is triangular and are about 3 to 6 inches long by 3 inches wide. Leaflets that grow on the stalks are lobed. The lower surface of the leaves are pubescent, with short curved hairs. The fern spreads by rhizomes that form a mat an inch below the surface.
The Japanese climbing fern can cover shrubs, the ground and tall trees because the rhizome root system allows them to grow in dense mats. The mats can grow as thick as 10 feet, and in turn, smother native plants and trees. Also, Lygodium japonicum can intensify fires because their climbing nature carries the fire up into the tree canopy. In Florida alone Lygodium japonicum has threatened three native and endangered plant species. One being a perennial shrub called Georgia bully, a wooly Dutchman’s pipe (a vine), and a branch tearthumb (herbaceous flowering plant). Since the tiny spores are so small and easily dispersed this fern is difficult to control. Also it is expensive to treat and persistent in re-growth after treatment. In 2000, the costs for eradicating this fern ranged from $135-500 per acre to $1,520 per acre in remote locations; by 2001 it had to be treated again.
The Japanese climbing fern reproduces by wind-dispersed spores that can be carried long distances by vehicles or other objects. Spores usually germinate within 7 days but dried spores can germinate after two years. The rhizomes allow the plant to spread locally and they can re-sprout after winter frosts or after vines are burned.
Lygodium japonicum have been cultivated in Florida as garden plants, and was offered in a nursery catalog as early as 1888. By 1903, it was naturalized in Georgia. Unfortunately, the species is still for sale on the Internet.
Eastern Asia, from India to Japan.
U.S. Habitat: This fern is limited to temperate and tropical areas, usually in damp or disturbed sites regardless of sunlight. However, it is not considered a wetland species and is commonly found alongside roads and in yards.
U.S. Present: AL, AR, FL, GA, HI, LA, MS, NC, PA, PR, SC, TX
The Japanese climbing fern resembles the invasive Old World climbing fern (Lygodium microphyllum) and the endangered American climbing fern (Lygodium palmatum).
The main way to minimize the dispersal of the Japanese climbing fern it to prevent spore formation. This can be done by not driving machinery though the fern areas or by not having workers work in several areas in one day. Small areas may be managed by hand pulling; but those plants also reproduce by rhizomes so even the smallest piece left behind can re-sprout. As mentioned before, the ferns just accelerate fires so that is not a viable option for management. Little work has been done on chemical control but several kinds of herbicides seem to be effective. However, because they cover other plants the chemical treatments can end up kill the trees and shrubs the ferns are climbing on. Research is currently looking into biological controls for this fern; but some are not a species specific as they need to be and can also attack the American climbing fern. Potential biological controls are able to be effective against the Japanese climbing fern and the Old World climbing fern. Possible biological controls include a defoliating moth (Neomusotima conspurcatalis) from Australia and Southeast Asia, and while it attacks the Japanese climbing fern it is not a threat to the American climbing fern; and another defoliating moth (Austromusotima camptozonale). The latter was released but it was not able to establish itself in America. Additional possibilities are a gall mite (Floracarus perrepae), a Lygodium-specific saw fly (Neostrombocerus sp.) and flea beetles (Manobia sp.)
Hutchinson, J. T., & Langeland, K. A. 2010. Review of two non-native, invasive climbing ferns (Lygodium japonicum and L. microphyllum), sympatric records and additional distribution records from Florida. American Fern Journal, 100(1):57-66.
Leichty, E. R., Carmichael, B. J., & Platt, W. J. 2011. Invasion of a Southeastern Pine Savanna by Japanese Climbing Fern. Castanea, 76(3):293-299.
Lott, M. S., Volin, J. C., Pemberton, R. W., & Austin, D. F. 2003. The reproductive biology of the invasive ferns Lygodium microphyllum and L. japonicum (Schizaeaceae): implications for invasive potential. American Journal of Botany, 90(8):1144-1152.
Minogue, P. J., Jones, S., Bohn, K. K., & Williams, R. L. 2009. Biology and Control of Japanese Climbing Fern (Lygodium japonicum).
Woodward, Susan L., and Joyce Ann. Quinn. 2011. Japanese Climbing Fern. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood, 2011. 597-99. Print.