Outside of its native range the Japanese fern vine can be a major pest due to its habit of smoothering adjacent plants beneath its dense growth like a smaller-scaled kudzu vine (Pueraria lobata).
Description Lygodium microphyllum is a luxuriant bright green fern with wiry dark brown stems that twine through trees and shrubs permitting the foliage to form kudzu-like draperies over other plants. The fronds may grow 100' or more into the treetops. The pinnate leaves (pinnae) that extend off the main stem (rachis) are 2-5" long and composed of tiny leaflets (pinnules) that are shaped like elongated hearts. These are borne alternately on distinct stalks. The fertile leaflets are distinctively fringed with extensions of rolled leaf tissue that cover the spore producing organs.
The more cold tolerant Japanese climbing fern (Lygodium japonicum) is very similar, but has many twice compound pinnae and more sharply pointed dissected leaflets, which give it a generally lacier and more delicate appearance. When the leaflets drop off old world climbing fern, they leave their stems behind, whereas Japanese climbing fern leaflets take their stems with them as they fall.
These are fertile leaves of Lygodium japonicum. The spore are borne on the underside edges of the leaflets.
Old World climbing fern is native to the region from Africa to Southeast Asia, the South Pacific, and Australia. It is widely naturalized in South Florida, where it tends to become established along the ecotonal transitions between pinelands and wetlands.
Vegetative growth and spore production continue year round so long as warmth and moisture are available.
Light: Climbing fern tolerates shade, but generally produces spores only on portions of the plant exposed to the sun. Moisture: Climbing ferns like damp soil. Hardiness: USDA Zones 8 - 11. Japanese climbing fern is more cold hardy, growing also in Zone 8 while old world climbing fern is more tender and grows only in Zones 9 - 11. Propagation: The climbing ferns germinate from spores in 6-7 days. Spores generally remain viable for several months.
These are the sterile leaves of the Japanese climbing fern (Lygodium japonicum). Although an obnoxious invader Florida and similar climates, this tough vine can lend an enthusiastic tropical tone to indoor landscapes and conservatories.
Climbing fern is used to enhance tropical atmosphere in atrium gardens, interiorscapes and landscapes in its native range (see Warning below).
Climbing ferns are tough. They grow back readily after droughts, freezes, and fires. If cut back, old world climbing fern can resprout from almost any point along one of its vinelike leaves. These plants are best used to create lush tropical atmosphere in northern greenhouses and atriums where their spores cannot escape to establish weedy infestations.
Old world climbing fern is an extremely destructive invasive species -- and the more northern Japanese climbing fern isn't much better. Both are listed as alien invaders by the Plant Conservation Alliance and as Category I invasive exotic species by the Florida Exotic Pest Plant Council. This means that they are known to be "invading and disrupting native plant communities in Florida." L. microphyllum is a noxious agricultural weed in Southeast Asia and an extremely troublesome pest plant in South Florida natural areas, where it forms dense blankets that smother native vegetation. The climbing ferns cause wildland fires to be inordinately devastating because they burn readily and carry flames across swamps and high into the tree canopy. L. japonicum is recognized as a weed in the Philippines and Taiwan and has become widely naturalized in central and northern Florida and across the Gulf coastal plain to Texas. In many places, it too has formed tree choking draperies over native vegetation.