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Giant Salvinia - Salvinia molesta

giant salvinia

Giant Salvinia© Barry Rice

Giant Salvinia is on the list of worst pests by The Nature Conservancy's North Carolina coastal region. It is classified as a Federal Noxious Weed and a North Carolina Class A Noxious Weed.

Giant salvinia (Salvinia molesta) is a very invasive free-floating fern from South America. Salvinia molesta can greatly alter our aquatic ecosystems. The mature plants weave themselves into a thick floating mat that excludes oxygen and light. Plants beneath the thick mats die. Fish survive only below the lip of the salvinia mat and in the open water beyond the mats. Waterfowl have difficulty in finding food. Reptiles, amphibians, and other aquatic animals that need oxygen move away or die. Hydroelectric plants and municipal, industrial, and agricultural water intakes will have problems with fouling. Swimming and boating are impossible in Salvinia mats. The U.S. Department of Agriculture listed the plant as a noxious weed in 1983.

Much of the Salvinia escaping to the wild has come from water gardens, nurseries, mail order plant suppliers, and water gardeners who swap plants with their friends and neighbors. Most of these people do not understand that Salvinia molesta can seriously degrade our water bodies.

Salvinia molesta varies in color from green to gold. The leaves of the young plants are the size and shape of fingernails and tend to lie flat upon the water. Large leaves may grow to two inches or more. Giant salvinia can double its mat size in 7 to 10 days. As the mats continue to grow, they form thick layers of vegetation.

The NC Division of Water Resource Aquatic Weed Program and the Wilmington office of the Corps of Engineers are cooperating to look for giant salvia in 17 counties between Interstate 95 and US Hwy 70. So far, giant salvia has been reported from Pender, Onslow, and New Hanover counties. There is special concern about its introduction to the Lumber River. 

 

Photograph: Barry A. Rice/TNC