Common Salvinia

Ecological Threat: The common salvinia is an aggressive invader that forms dense mats, which prevent light from reaching native plant and fish species. The lack of light resources reduces dissolved oxygen levels in the water causing death and decay of native species. Agricultural water use is impacted as salvinia obstructs intake pipes for irrigation. Recreational fishing and boating is also prevented by dense salvinia growth.
Biology & Spread: The common salvinia reproduces via spores or fragmentation, which is consistent with other fern species. U.S. populations of common salvinia commonly reproduce via fragmentation from both attached nodes or broken stems. As many as five lateral buds can be found at one node. Rapid expansion has been recorded with populations doubling every 2 weeks in the wild. Small ponds have been completely covered with giant salvinia in as little as 6 weeks after invasion.

History:
One source says the introduction of common salvinia is believed to have occurred in the 1880's as a agricultural plant cultivated in greenhouses and gardens. It is believed to have become established via natural flooding of private ponds and pools in the 1920's in Florida.
Another source says it was first noted in the U.S. in St. John's river in eastern Florida, and thought to have been transported there by shipping boats in the late 1920s or early 1930s.
Currently, growth and distribution is only prohibited in Texas and Louisiana.

- See more at: http://www.tsusinvasives.org/database/common-salvinia.html#sthash.7C3r3…