Japanese Climbing Fern (Lygodium japonicum)
(Thunb. ex Murr.) Sw.
Miller, J.H., E.B, Chambliss, N.J. Loewenstein. 2010. A Field Guide for the Identification of Invasive Plants in Southern Forests. General Technical Report SRS-119. Asheville, NC. United States Department of Agriculture, Forest Service. 126 p.
Perennial viney fern, climbing and twining, to 90 feet (30 m) long, with lacy finely divided fronds along green to orange to black wiry vines or rachis, often forming infestations of shrub- and tree-covering mats. Tan-brown fronds persisting in winter, while others remain green in FL and in sheltered places further north. Vines arising as branches (long compound leaves) from underground, widely creeping rhizomes that are slender, dark brown, and wiry.
Slender but difficult to break, twining and climbing, wiry. Green to straw colored or reddish. Mostly deciduous in late winter except in south FL.
Leaves (fronds or pinnae)
Opposite on vine, compound, once or twice divided, varying in appearance according to the number of divisions, generally triangular in outline. Three to 6 inches (8 to 15 cm) long and 2 to 3 inches (5 to 8 cm) wide. Highly dissected leaflets, appearing lacy, especially fertile ones. Light green turning tan to dark brown in winter.
Fertile fronds have smaller segmented fingerlike projections around the margins, bearing sporangia (spore producing dots) in double rows under margins.
Late summer to fall (year-round in south FL). Tiny, wind-dispersed spores.
Occurs along highway right-of-ways, especially under and around bridges, invading into open forests, forest road edges, and stream and swamp margins. Scattered in open timber stands and plantations, but can increase in cover to form mats, especially after burns, smothering shrubs and trees. Creates “fire ladders” to carry fires upward to scorch and damage canopies of shrubs and trees. Persists and colonizes by rhizomes and spreads rapidly by wind-dispersed spores that are also transported in pine straw mulch and on clothing. Dies back in late winter in the more northern areas, with dead vines providing a trellis for reestablishment.
Resembles Old World climbing fern [L. microphyllum (Cav.) R. Br.] and American climbing fern [L. palmatum (Bernh.) Sw.], both of which are distinguished by 5 to 7 palmately lobed, fingerlike fronds. American climbing fern—a native occurring in swamps, streambeds, and ravines—does not spread beyond small areas to form extensive infestations. Old World climbing fern, also introduced, is a major invasive pest in mid- to southern FL and projected to migrate northward.
History and use
Native to Asia and tropical Australia and introduced to FL from Japan in the 1930s. An ornamental still being spread by unsuspecting gardeners.
Found in dense infestations in southeast TX; south and central LA; central and north FL; and spreading north through AR, MS, AL, and GA. Scattered infestations further north from ornamental plantings in cities and towns.
- Do not plant. Remove prior plantings, and control sprouts and seedlings. Bag and dispose of plants in a dumpster or burn.
- Treat when new plants are young to prevent spore formation.
- Clean shoes, clothes, dogs, and equipment before leaving infested areas. Tiny spores can hitchhike, so extreme care must be used to prevent spread.
- Minimize disturbance within miles of where this plant occurs, and anticipate wider occupation when plants are present before disturbance.
- Burning treatments can worsen infestations and result in tree damage due to fire ladders.
Recommended control procedures
- Thoroughly wet all leaves to as high as safe with one of the following herbicides in water with a surfac-tant (July to September before spore release), avoiding spray to nontarget plants: a glyphosate herbicide as a 4-percent solution (1 pint per 3-gallon mix) directed at the fern to minimize nontarget damage or Escort XP at 1 to 2 ounces per acre in water (0.3 to 0.6 dry ounce per 3-gallon mix) and as a mixture with a glyphosate herbicide,
- When nontarget damage is not a concern, apply Arsenal AC as a 1-percent solution (4 ounces per 3-gallon mix).