Plants and Planting

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Plants and Planting

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 Plants contribute to the esthetic appetence of a constructed wetland and attract a plethora of wildlife, but in warmer climates plants can also assist in the remediation of wastewaters through nutrient uptake for their growth. There are also certain types of plants that have been shown to be very efficient phytoremediators, and can sequester heavy metals and other toxins within their structures such as the Chinese Ladder fern Pteris vittata, which is a highly efficient accumulator of arsenic. The plants must be harvested periodically to prevent the sequestered nutrients, and metals from reentering the system as the plant dies back. The roots of plants also add to the substrate for microbial biofilm development, and the additional oxygen that is pumped to the roots by the plants helps to oxygenate the rhizosphere and may facilitate oxygenic and facultative microbial respiration of potential pollutants. The uses of exotic plants to perform remediation functions in constructed wetlands can be problematic due to the possibility of the plant escaping and displacing indigenous species in natural systems.
  
In cold climates plants have been shown to have a very limited effect on a constructed wetlands ability to remediate wastewater so little in fact that some experimental designs and even some full scale systems have omitted them as an unnecessary expense or may allow natural vegetation to colonize the wetland to act as an insulation barrier during cold winters.

http://www.iridra.it/index_eng.htm
Given this lack of functionality of plants it allows for grate range of versatility for the essential beautification and habitat creation that substantially increase aesthetic value of an artificial wetland over a conventional wastewater treatment facility.

Plants are especially vulnerable to wetland destruction as they are not motile, and rely on seed dispersal to move from one area to another to propagate their species. Constructed wetlands can provide a haven for endangered species. Hybrid designed wetlands offer a diverse habitat that can be planted for conservation or esthetic values and can encompass a large range of plant species form emergent at totally submerged plants.

Two especialy endangered wetland plans that could be protected by propigation in constructed wetalnds
            
Furbish's Lousewort (Pedicularis furbishiae)
An endangered species found only in Maine and New Brunswick On the bank of the St. John River in northern Maine Furbish's Lousewort may benefit form being propagated around surface floe constructed wetlands.



Eastern Prairie Fringed Orchid Platanthera leucophaea
The distribution of the Eastern Prairie Fringed-orchid is centered around the Great Lakes, and the orchid reaches the northern extent of its range in southern Ontario.
Estimates reported in 2003 are based on maximum counts made over the 1990s, and indicate that there are about 1050 Eastern Prairie Fringed-orchids across 20 populations in southern Ontario. There are also 14 known historical sites from which the orchid is extirpated. The Eastern Prairie Fringed-orchid grows in wet prairies, fens, bogs, and occasionally old fieldshttp (http://ecos.fws.gov/species_profile/SpeciesProfile?spcode=Q2GG).
UVM NR260: Wetlands Ecology and Management
Contact: mcunning@uvm.edu, University of Vermont
Page created/updated: 02/10/2006