Practical information to identify and manage non-native, invasive plants and animals
The Quiet Invasion:
A Guide to Invasive Species of the Galveston Bay Area
Giant salvinia, kariba weed; Common salvinia, water spangles
Salvinia molesta; Salvinia minima

USDA Symbol:SAMO5; SAMI7
ITIS TSN:181823; 181822
Presence:Current Invaders
Habitat:Aquatic
Native Range:South America
Toxic Characteristics
These species are not known to be toxic.
Geographic Distribution
Giant salvinia has been reported from Virginia to California as well as Hawaii, but the majority of infestations currently exist in Texas and Louisiana. Locally it is found in water bodies in Friendswood, League City, Alvin, Houston, Channelview, Mont Belvieu as well as in the Sheldon Lake State Park and Trinity River National Wildlife Refuge. Common salvinia occurs from South Carolina to East and Central Texas. No known populations in the Houston-Galveston region.
Introduction Pathways
Common salvinia was long considered to be native to the U.S. However, it was most likely introduced to the US in the 1920s. Giant salvinia is a popular aquarium plant. It was first detected outside of aquarium and landscape cultivation in South Carolina in 1995, was found in Texas in 1997, and rapidly spread to other southern states over the following years.
Specific Primary Habitats
Salvinia thrives in slightly acidic, high nutrient, warm, slow-moving freshwater. Found in streams, lakes, ponds, ditches, and even rice fields. Resistant to periods of low temperature, dewatering, and elevated pH levels. Low tolerance to salinity.
Identifying Characteristics
Salvinia is a rootless, aquatic fern. Emergent groups of leaves (fronds), oblong and flat or semi-cupped, grow in chains and float on the water surface forming dense mats. Leaves grow in pairs and are approximately 1/2 inches wide and 1 inch long. A brown, thread-like leaf hangs underwater; all join at a node along a horizontal, underwater stem. The upper surface of the green leaves is covered with rows of white, coarse hairs, acting as a water repellent. The hairs of giant salvinia are joined at the tips in an egg beater shape. Hairs of common salvinia are unjoined at the tips. Fruits (sporocarps) are egg-shaped and grow in chains underwater.
Reproduction Characteristics
While Salvinia may reproduce via spores as other ferns do, U.S. populations more commonly reproduce via budding from both attached nodes or broken stems. As many as five lateral buds can be found at one node.
Growth Characteristics
Populations can double every 2 weeks in the wild, and small quarter-acre ponds have been completely covered with giant salvinia in as little as 6 weeks from the point of invasion.
Ecological, Economic, or Social Impact
Dense mats of salvinia shade out native aquatic species and reduce dissolved oxygen levels in the water. Agricultural water use is impacted as salvinia obstructs intake pipes for irrigation. Recreational fishing and boating may be hindered by dense mats.
Control
The best control is to prevent further infestations. Enclose harvested biomass and dispose in upland areas away from water. Herbicides (copper carbonate or Rodeo) are necessary for large populations. Biocontrol (Salvinia weevil) may also be effective.

Native Species Alternatives
Below is a list of alternative plants that are native to the area:
  • American lotus (Nelumbo lutea)
  • White water lily (Nymphaea odorata)
  • Floating heart (Nymphoides aquatica)
This species belongs to the following lists:
Images
To view a larger version of an image, click on the thumbnail.
Hairs of the giant Slavonia form an 'egg-beater' shape at the tips. Photo courtesy of Rebecca Davey, Commonwealth Scientific and Industrial Research Organization, www.forestryimages.org; Image Number 0002106.
Hairs of the giant Slavonia form an 'egg-beater' shape at the tips. Photo courtesy of Rebecca Davey, Commonwealth Scientific and Industrial Research Organization, www.forestryimages.org; Image Number 0002106.
Leaves of the giant Salvinia plant. Photo courtesy of USDA APHIS Archives, USDA APHIS, www.forestryimages.org; Image Number 1148172.
Leaves of the giant Salvinia plant. Photo courtesy of USDA APHIS Archives, USDA APHIS, www.forestryimages.org; Image Number 1148172.
Giant Salvinia at the water surface with both live and dead leaves. Photo courtesy of Scott Bauer, USDA Agricultural Research Service, www.forestryimages.org; Image Number 1317055.
Giant Salvinia at the water surface with both live and dead leaves. Photo courtesy of Scott Bauer, USDA Agricultural Research Service, www.forestryimages.org; Image Number 1317055.
Herbicidal control of the giant Salvinia plant. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333003.
Herbicidal control of the giant Salvinia plant. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333003.
A large infestation of giant Salvinia in Mississippi in mid-August. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333010.
A large infestation of giant Salvinia in Mississippi in mid-August. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333010.
A large infestation of giant Salvinia in Mississippi in late September. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333011.
A large infestation of giant Salvinia in Mississippi in late September. Photo courtesy of Kenneth Calcote, Mississippi Department of Agriculture and Commerce, www.forestryimages.org; Image Number 1333011.
Page Updated/Reviewed: 07/14/2010 8:33 AM
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