Old World Climbing Fern (Lygodium microphyllum), a Dangerous Invasive Weed in Florida

Abstract

-Lygodium microphyllum, a native of the warm and wet regions of the Old World, was first detected to be naturalized in southeastern Florida in 1965. This fern has become an aggressive invader of natural vegetation in many different habitats that are frequently dominated by the weed. Aerial surveys conducted in 1993, 1995, and 1997 detected increasing densities and continued expansion of its distribution in Florida. The fern is expected to continue to increase in Florida and could spread by spores to suitable habitats in Texas and Mexico. No effective method of control for the plant exists. Lygodium microphyllum (Cav.) R. Br. (Schizaeaceae), or Old World climbing fern, is native to wet tropical and subtropical regions of the Old World. It has become a serious weed in southeastern Florida, where it is increasing in density and range. In the present paper we discuss the ecological problems associated with the fern and its naturalization and spread, probable origin, and potential to spread, and the control attempts to date. The companion paper (Pemberton, 1998) discusses the potential of biological control to reduce populations of this plant and to limit its spread. The fern's native distribution and taxonomic relations, both essential information for a biological control program, are also reported.