Tuberous sword fern
Florida is host to many non-native species, both plant and animal in origin. Nephrolepis cordifolia, or sword fern, is a plant that was introduced most likely for its ornamental attributes. In 23 counties from the Gainesville area south, specimens of sword fern have been found and documented. Now considered a Category I invasive species, sword fern has made its presence known and continues to spread across Florida.
Nephrolepis cordifolia is a wood fern that typically grows in woodland areas. Both fertile and sterile fronds are pinnate, up to 3 feet in length and 3 inches wide. There are many leaflets, or pinnae, ranging from 40-100 mm (1.5 to 4 inches) on each side of the rachis. Each pinna is oblong to lanceolate with an auricle that overlaps rachis. Rhizomes are orange/brown to pale brown with linear scales having hair like tips. Stolons are straw colored and produce small underground tubers. The presence of tubers distinguishes sword fern from the native Nephrolepis exaltata fern. Numerous sori (spore containing structures) are also produced between the leaflet midvein and margin. Dispersal occurs via spores and through the movement of stolons, tubers, and rhizomes.
The sword fern poses a threat on native species. Through its aggressive spread, sword fern is able to form dense stands and quickly displace native vegetation. Because it is a true fern, it reproduces via spores. Thousands of spores can be produced by one plant and these can be dispersed by wind and water. Spore production occurs year-round in south Florida.
The first step in preventative control of sword fern is to limit planting and removal of existing plants within the landscape. If possible, removal should occur before spores are produced.
Plant native or non-invasive alternatives. Inform the public to refrain from purchasing, propagating, or planting sword fern due to its ability to escape from cultivation. Avoid transport of spores from one area to the next via people, vehicles and other equipment.
Hand pulling can be used to remove some of the fern plants, but the plants will break off, leaving plant parts in the ground from which regrowth will occur. Be sure to dispose of plants properly.
There are no known biological agents for the control of sword fern.
Plants can be killed with herbicides containing glyphosate. A foliar application of a 1.5% solution provides good control. Follow-up applications are necessary to control plants regrowing from rhizomes and tubers.