Japanese Climbing Fern
Lygodium japonicum (Thunb. ex Murr.) Sw.

Miller, James H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. Gen. Tech. Rep. SRS–62. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p.

Plant. Perennial viney fern, climbing and twining, to 90 feet (30 m) long, with lacy finely divided leaves along green to orange to black wiry vines, often forming mats of shrub- and tree-covering infestations. Tan-brown fronds persisting in winter, while others remain green in Florida and in sheltered places further north. Vines arising as branches from underground, widely creeping rhizomes that are slender, black, and wiry.

Stem. Slender but difficult to break, twining and climbing, wiry. Green to straw-colored or reddish. Mostly deciduous in late winter.

Leaves (fronds). 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 leaves, appearing lacy. Light green turning dark to tan brown in winter.

Flowers. Fertile fronds usually smaller segments with fingerlike projections around the margins, bearing sporangia (spore producing dots) in double rows under margins. Seeds. Tiny, wind-dispersed spores.

Ecology. 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, smothering shrubs and trees. Persists and colonizes by rhizomes and spreads rapidly by wind-dispersed spores. Dies back in late winter 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 five to seven palmately lobed, finger-like fronds. American climbing fern—a native occurring in swamps, stream beds, and ravines—does not spread beyond small areas to form extensive infestations. Old World climbing fern, also introduced, is a major invasive pest in southern Florida.

History and use. Native to Asia and tropical Australia and introduced from Japan in 1930s. An ornamental still being spread by unsuspecting gardeners.

Recommended control procedures:

Thoroughly wet all leaves with one of the following herbicides in water with a surfactant (July to October):

• Arsenal AC* as a 1-percent solution (4 ounces per 3-gallon mix)
• Garlon 3A, Garlon 4, or a glyphosate herbicide as a 2-percent solution (8 ounces per 3-gallon mix)
• Escort* at 1 to 2 ounces per acre in water (0.3 to 0.6 dry ounces per 3-gallon mix)

*   Nontarget plants may be killed or injured by root uptake.

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