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Old World Climbing Fern
old world climbing fern
Old world climbing fern, photographed at John Prince Park, Lake Worth, Palm Beach County.
old world climbing fern  

Old world climbing fern, lygodium microphyllum, is a double threat. It is an invasive, capable of smothering trees and shrubs and choking out native orchids, bromeliads and a host of understory plants. It can swallow tree islands whole, figuratively speaking. But what makes this plant especially dangerous is fire. This fern can act as a ladder that enables brush fires to reach the upper canopies of forests.

Old World is found in swamps, wetlands, wet meadows and hammocks of Florida's peninsula from Brevard and Hillsborough counties southward. As you might guess, it is a major ecological threat anywhere it's found — only in Florida now, but Texas and Louisiana are believed to be vulnerable as are the Caribbean, Central Ameria and South America. It is listed as a noxious weed in Alabama, Florida and by the federal government.

It is a native of Africa, Southeast Asia, Australia and the South Pacific, and came to this country as an ornamental. By 1960, naturalists found the first specimens of old world growing in the wild. The Institute for Regional Conservation believes it is being cultivated still.

It spreads three ways — by rhizomes, or stems that grow along the ground or just under it; by spores; and by its climbing leaves, which can resprout when clipped from the main plant. It produces spores by the zillions, which can be distributed many, many miles by the wind, particularly during storms, by animals and by humans when the spores attach themselves to clothing and equipment. It produces spores year round, but peaks during the fall — September to November.

 
 
old world climbing fern
 

Old world climbing fern can be huge; its climbing leaves can reach 90 feet or more (a cousin, Japanese ciimbing fern, Lygodium japonica, can reach 100 feet or more). It can form dense mats, four feet thick or more. It has two types of leaves, one that is arrow-shaped and infertile, and another that is ornately lobed and produces spores. The spore-bearing leaves tend to be more numerous where the plant gets the most sunlight. Not only is the plant a fire hazard, it seems to be fire tolerant. One scientist burned a plant with a propane torch. It resprouted.

The best way to control the spread of old world climbing fern appears to be pulling new infestations as they develop. Of course that can be a bit of a challenge in places like Everglades National Park or Loxahatchee National Wildlife Refuge, which extend over hundreds of thousands of acres. Biological controls are being tried, including unleashing the larvae of a bug from Australia that eats old world climbing fern leaves. Old world climbing fern is a member of the Lygodiaceae family.

Photographs by David Sedore
     
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