Old World climbing fern: Lygodium microphyllum

Appearance:

The correct name of Old World climbing fern is L. microphyllum, but the species is occasionally referred to as Lygodium scandens. As many as 40 species have been placed in the genus Lygodium, but a recent revision has reduced this number to 26. Lygodium japonicum, another invasive species in the southeastern United States, has leaflets that are more dissected and lobed than those of Lygodium microphyllum.

Look for first

• tangle of wiry, twining fronds
• fern-type leaflets
• sporangia under curled leaflet margins

	Leaves: Twining fronds of indeterminate growth to 30 m (90 ft.) long. Leafy branches off main rachis (constituting the pinnae) once compound, oblong in overall outline, 5-12 cm (2-5 in.) long. Leaflets (pinnules) usually unlobed, stalked, articulate (leaving wiry stalks when detached); leaf-blade tissue usually glabrous below; fertile leaflets of similar size, fringed with tiny lobes of enrolled leaf tissue covering the sporangia along the leaf margin.
	Stems: Fern with dark brown, wiry rhizomes forming layered mats or canopies over existing vegetation.
	Flowers: None. Ferns are a spore-releasing class of vascular plants.
	Spores: Many thousands of tiny spores released per plant and carried by wind, dust, animals, clothes, and equipment.

Habitat:

Old World climbing fern is an aggressive nonnative invasive fern of moist habitats in South Florida. This rapidly spreading fern invades new areas without the need of habitat disturbance and often completely dominates native vegetation by forming a dense canopy. The fern, first found to be established in 1965 in Martin County, now infests more than 200,000 acres in South Florida.

Distribution

Native to Africa to Southeast Asia, South Pacific islands, and Australia. In Florida, most common in South Florida but spreading into Central Florida.

Behavior:

Although primarily a weed of public conservation areas, Old World climbing fern infests residential landscapes, horticultural nurseries, rangelands and other managed lands near infested natural vegetation.  The fern's ability to grow up and over trees and shrubs and to form dense horizontal canopies
allows it to cover whole communities of plants reducing native plant diversity. Old World climbing fern can grow in bald cypress stands, pine flatwoods, wet prairies, saw grass marshes, mangrove communities and Everglades tree islands. Some Everglades tree islands are so completely blanketed by the fern that it is not possible to see trees and other vegetation beneath the fern canopy. The fern poses management problems for both wildfires and prescribed burns because it can serve as a fire ladder that carries fire into the tree canopy that kills native trees. Also, portions of burning fern can frequently break free and spread fire to surrounding areas.  Scientists' estimate that, left unchecked, Old World climbing fern could infest more than 2 million acres in South Florida by 2014.

Why the Old World climbing fern must be managed

• Highly invasive in natural areas.
• Severe threat to Everglades tree island communities
• A canopy producer that smothers native trees and shrubs.
• Can serve as a fire ladder that carries fire into native tree canopies that normally wouldn't burn.
• The fern is rapidly spreading in South Florida's public conservation lands.

Additional Information:

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Old World climbing fern (Lygodium microphyllum)

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Image Credit: Center for Aquatic and Invasive Plants, University of Florida