Nonindigenous Aquatic and Semi-Aquatic Plants in Freshwater Systems

Nonindigenous Aquatic Plants

Water Sprite, Water Hornfern, Oriental Waterfern (Ceratopteris thalictroides; L.) Brongn.

Water sprite (Fig. 16) is a native of tropical East Asia and Australia (Muhlberg 1982; Sainty and Jacobs 1981). It was first cultivated as an ornamental in England in 1834 and remains widely popular for aquaria and outdoor gardens. All parts except the roots are edible (Sainty and Jacobs 1981). Two species of Ceratopteris occur in Florida; C. pteridoides and C. thalictroides. Ceratopteris pteridoides is presumed native to the state, whereas C. thalictroides has a much wider distribution and may be introduced (Schardt and Schmitz 1990). Circumstances surrounding the entry of water sprite into Florida are unclear; however, it was first reported in southwestern Florida in 1878 (Small 1931).

Water sprite is floating, submersed, or emersed; the two latter forms are usually rooted to muddy soils. This delicate fern is in static or slowly moving, acidic (pH 5.0-6.5), and soft waters (Rataj and Horeman 1977). Reproduction is by spores that germinate readily on muddy soils (Rataj and Horeman 1977).

The two species of water sprite were in 28 waters where they covered 11 ha and ranked 100th in abundance of aquatic plants recorded in public waters during 1990. They rarely cause water-use problems (Schardt and Schmitz 1990). Both species are usually innocuous.