Nonindigenous Aquatic and Semi-Aquatic Plants in Freshwater Systems

Nonindigenous Aquatic Plants

Taro (Colocasia esculenta; L.) Schott.

Taro (Fig. 9) in the Americas is from French Tropical Africa and was brought in as a staple food crop by slaves. Its origin is in India and in Southern Asia. It was an important food source in the Nile Valley (Begley 1979). The variety of the most familiar taro in Florida was introduced by the U.S. Department of Agriculture in 1910 as a substitute for potatoes that did not grow well in the moist soils of the Southeast (Greenwell 1947). As recently as 1982, experiments to grow taro for food or fuel in the Everglades Agricultural Area were partially funded by the South Florida Water Management District (Shih and Snyder 1984). Taro was in 183 public waters during 1990, covered 371 ha, and ranked 51st in abundance of all reported aquatic plants (Schardt and Schmitz 1990).

Taro can grow in a wide range of sites from dry uplands to wetlands with soils that remain saturated for prolonged periods (de la Pena 1983). It is emersed along moist, shaded lake and river shorelines and tolerates intense sunlight to deep shade. Reproduction is primarily vegetative. Seed production is thought to be uncommon, and seeds and seedlings have low viability (Nyman and Arditti 1985). Taro displays allelopathic characteristics (Perdales and Dingal 1988) and contains a toxin (calcium oxalate crystals) that can deliver a mild sting or even a severe rash (Greenwell 1947). Cooking before ingestion eliminates much of the irritation (Schardt and Schmitz 1990).

Although it is a nuisance species, problems by taro are uncommon and are usually associated with environmental concerns rather than human activities. Taro can grow densely along lake and river margins where it crowds out native vegetation. Mechanical harvesting or mowing does not control taro because regrowth from the corms is quick. Repeated treatments with 2,4-D or 2,4-D and glyphosate provide acceptable temporary results; however, physical removal of the corms is required for eradication from aquatic sites (Schardt and Schmitz 1990).