Nonindigenous Aquatic and Semi-Aquatic Plants in Freshwater Systems

Nonindigenous Aquatic Plants

Parrot-Feather (Myriophyllum aquaticum; Vell.) Verdc.

This member of the milfoil family (Fig. 14) is generally thought to be native to South America (Nelson and Couch 1985), although its origin is sometimes assigned to Brazil (Fernald 1950). Parrot-feather is named for the feather-like appearance of its gray-green, almost iridescent leaves.

Aquarists were responsible for introducing this plant worldwide (Nelson and Couch 1985) for an indoor and outdoor ornamental (Sutton 1985). Parrot-feather began appearing in the United States in the late 1800's and was first reported in Florida in 1906. Its subtropical origin is reflected by its distribution in the southern United States and along the West Coast. Many temperate introductions survived for short periods but did not persist (Nelson and Couch 1985).

Parrot-feather is relatively uncommon in Florida. It grows sporadically throughout the state, most often in enriched or degraded canals and ditches in southern Florida. Forty-eight of the public lakes and rivers surveyed in 1990 were hosts to a total of 19 ha of parrot-feather, which ranked 93rd in abundance of all aquatic plants. This submerged milfoil has emersed stems and grows in a variety of habitats from muddy soils to 1.8-m deep water (Schardt and Schmitz 1990).

Parrot-feather is listed as a problem weed in some parts of the world but is for the most part nonproblematic in Florida (Schardt and Schmitz 1990). Some experts consider this plant more beneficial than harmful in some environments (Sutton 1985). The herbicide 2,4-D (liquid and granular formulations) applied to young, growing plants provides the best control. Fewer than 2 ha are controlled each year in rivers and along lake shores in Florida (Schardt and Schmitz 1990).