Myriophyllum Aquaticum

''Myriophyllum aquaticum'' is a flowering plant, a vascular dicot, commonly called parrot's-feather and parrot feather watermilfoil.

Morphology and reproduction

Parrot feather is a perennial plant named for its feather-like leaves which grow in whorls of four to six around the stem. Its emergent stems and leaves are its most distinctive features, as they can grow up to a foot above the water's surface, resembling small fir trees. The woody emergent stems can grow to over 5 feet / 1.5m tall and will extend to the bank and shore. Pinkish-white flowers measuring approximately 1/16 inches long extend out from the plant. As the water warms in the spring, the species begins to flourish, and while most individuals flower in the spring, some also flower in autumn. Almost all plants of this species are female; in fact, no male plants have ever found outside of South America. Seeds are not produced by any North American plants. Parrot feather reproduces asexually. New plants grow from fragments of already rooted plants. The plant has whorls of feathery, blue-green to waxy, grey-green leaves that are deeply cut into many narrow lobes.

Kasselmann recently described a new variety, ''M. aquaticum'' var. ''santacatarinense'', which distinguishes itself from the typical variety by its more stiff and robust habitus and pinnae that are fewer and broader.

Habitat

Parrot feather is native to the Amazon River in South America, but it can now be found on every continent except Antarctica. It is thought that this plant was introduced to North America around the late 1800s. It was first discovered in the United States in the 1890s in Washington, D.C.Non-native Invasive Plants

Accessed 2011-11-10. Parrot's feather typically grows in freshwater streams, ponds, lakes, rivers, and canals that have a high nutrient content. During the 20th century it colonised areas in South Africa, Japan, England, New Zealand, and Australia. As it prefers a warmer climate, it is chiefly found in the southern parts of the United States.

Use and spread

Parrot feather is now used for indoor and outdoor aquatic use. It is a popular plant in aquatic gardens. It spreads easily and has become an invasive species and a noxious weed in many areas. The plant can be introduced to new areas when sections of its rhizome are dug up and moved. In Florida in the United States, flea beetles have been found to use parrot feather as a host for their larvae.

Ecological impacts

Due to its aesthetic appeal and ease of cultivation, parrot feather has been introduced worldwide for use in both indoor and outdoor aquaria. It is also a popular plant for aquatic gardens. However, it has escaped cultivation and spread via plant fragments and intentional plantings. While it may provide cover for some aquatic fauna, it can significantly impact the physical and chemical characteristics of lakes and streams. The parrot feather grows abundantly, shades out naturally occurring algae, and clogs irrigation ducts and canals. The parrot feather typically grows in bundles that extend out of the water. In large numbers, the plants form dense mats on the water's surface, which shades the water from sunlight, causing native plants to die due to light deficiency. Organisms that feed on the native plants may also die due to starvation. Moreover, the dense mats also cause problems for recreation. For example, swimmers and boat propellers can become entangled in the mats, which are also a potential breeding ground for mosquitos.

Clean-up efforts

The effect of herbicides in controlling the growth of this species has been found to be limited, partly due to the plant's waxy cuticle that acts as an effective barrier to the absorption of the poison. Cutting and chopping are also ineffective and can paradoxically facilitate the spread of the plant. In the U.S. states of Alabama, Connecticut, Massachusetts, Maine, Vermont, and Washington, parrot feather is a declared noxious weed and is therefore banned from sale.

The two main solutions to manage this aquatic nuisance is physically removing the plant and or using herbicides.

The physical aspects of removal are such acts of cutting, harvesting, and rotovation (underwater rototilling). These methods produce the best results only when the extent of the infestation has taken over all available niches. This is because of the availability of space as compared to rapid growth. Using physical control methods during the initial stage of plant infestation have been found to accelerate its rate of spread.

Another method of controlling Parrots feather is by the usage of herbicides. The herbicides are effective to the plant part exposed above water. The plant parts beneath the water never come fully into contact with the herbicides and are therefore washed away. Herbicides are most effective when applied to young growing plants. They should be applied repeatedly to show maximum results. ''M. aquaticum'' is more difficult to control with herbicides than other aquatic species. The leaves are protected by a thick waxy coating, and in order for herbicides to penetrate the leaves, surfactants must be added; however, herbicides may impact non-target native plants or animals.

In the United Kingdom, this plant is now classified as an invasive species and is one of five introduced aquatic plants that were banned from sale from April 2014. This is the first ban of its kind in the country.

In Europe, parrot feather has been included in the list of Invasive Alien Species of Union concern (the Union list) since 2016. This implies that this species cannot be imported, cultivated, transported, commercialized, planted, or intentionally released into the environment in the whole of the European Union.

References

External links

Jepson Manual TreatmentBerkeley Botany Photo of the DayTexas InvasivesInvasive Plant Atlas of the MidsouthPhoto gallery

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aquaticum
Freshwater plants
Flora of the Amazon
Plants described in 1825