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Giant Salvinia, Salvinia molesta

Scientific Name: Salvinia molesta
Common Name(s): Giant Salvinia


Research Summary
: Sarah C.

Salvinia molesta is something I have learned that you do not want where you live.  It was a difficult plant to research because it had multiple sources with not a lot of information and sources with information that I already had or something that I was not looking for.  Two things I found very surprising were that Salvinia molesta originated in Brazil and that it doubles every 2.2 days.  I think that the most important thing that I discovered while researching this species is that if you find it anywhere that it is not already present, you need to contact someone immediately and have it removed so that it does not become invasive to your clean water areas.

Identifying Characteristics
  • Aquatic ornamental plant.
  • Free floating fern: "rootless".
  • Rhizomes, "Mass of roots"


  • The leaves are green, yellow, and brown.
  • The upper parts of the green leaves are coated with white layers of hair.
  • The hairs may be broken on some leaves, but these specialized hairs create a water shield and a protected covering.
  • The leaves are .5 to 1.5 inches long or 2.5-3.8 cm long.



Taxonomy of Species
   Scientific Classification
 What That Classification Means
 Kingdom Plantae  Eukaryotic, one and many celled, don't move, members make their own
 food, non vascular and vascular.
 Phylum Pteridophyta  Containing all the vascular plants that do not bear seeds: ferns,
 horsetails, club mosses, and whisk ferns. 
 Class Filicopsida  Large, feathery leaves with spores on the underside of the leaves.
 Order Hydropsida (salviniales)  An order of ferns.
 Family Salviniaceae  Floating fern family.
 Genus Salvinia Seg.  Watermoss
 Species Salvinia Molesta  Kariba-weed

Similar species include: Hygrophila polysperma, Hydrilla verticillata

Location and Movement

Origin/ Native Range
 This plant is local to the coastal region of southern Brazil (24 degrees latitude and 32 degrees north) and South America.
Was first announced to North America as a ornamental plant.  Since the 1930's, Salvinia molesta spread all around the world!  It started to be recorded in the United States in 1995 from 19 plus locations in 41 freshwater places. Salvinia molesta was first recorded in the United States in South Carolina in 1995. It was found in a private pond on 1.5 acres. It was chemically removed within a year and has not been back for years.
Spread of Species  It will spread in many ways.  One way is that one plant will double every 2.2 days and in 30 days, you will have 8,000 new plants. Another way is that if you have a boat, and you boat through Salvinia molesta, it will break into parts and those parts will spread in to more.  It will spread if juts a splash of infested water touches some clean water area!
Where is it now invasive?
  • It is now found in the United States in... AL, AZ, CA, FL, GA, HI, LA, MS, NC, SC, TX, and DC.
  • It is also found in South Africa, Sri Lanka, India, Southeast Asia, Indonesia, Malyasia, Papua New Guinea, Australia, and the North Island of New Zealand.


Is this species in Maine?
 It was being kept in a greenhouse in Portland, ME in July of 2005, but it is not invasive here.  If it may get loose, there would be a possibility of it becoming invasive.  Other than that one cup of Salvinia Molesta, it is not invasive, or in Maine. This sample was destroyed by officials.
Where has it been identified?
  The closest state to Maine is Virginia.
How was this species introduced?



Natural Environment
  •  Likes to live in lakes, ponds, ditches, streams, swamps, rice fields, marshes, and oxbows.
  •  Doubles every 2.2 days and 1 plant becomes 8,000 in 30 days, after 2 months, you will have 67,000,000 plants, and by 4 months, you will have 4,500,000,000,000,000 plants.
Climate and Temperature Range
Salvinia molesta can not grow in any areas below 5 degrees Celsius and above 43 degrees Celsius. The best growth rate is at 30 degrees Celsius.


Ecological Interactions  Producer
 It gets it's nutrition by absorbing its food through a process called photosynthesis.
Consumed By
 Eaten by the black weevel, and the grass carp.


 Ecological Blocks sun and energy from getting to under the water, so living things under the water (for example: algae) cannot photosynthesize and get nutrients they need.  Fish and birds migrate away because it is so bad they can not live with it or they will die.
 Human You can't boat in infested waters or the weeds will break apart into new weeds and spread in to more.  Also, can clog the drinking water and the irrigation lines.
 Economic  It may cost money if you have a bad infestation and need herbicides or toxicants. courently,  organizations have been cuting back on toxicants, but if it gets extremely bad, they will use them.  Also, we may need to pay to ship black weevels to get rid of an infestations.


 Biological Grass carp will eat it, but they do not take total control.  The black weevel will stop spreading and reduce populations. 

Big infestations usually need use of commercially available herbicides with also the biological control organisms,

but it has lately been tested without using chemicals in addition to the biological control.

 Mechanical/ Manual
Experts use methods like hand and machinery removal.  They also block it in or out of areas where it can or cannot be with floating booms.
Boaters can make sure that no plant is caught up in the boat. Jet washing and visual inspections can help detect weeds parts on the boats.  
 Chemical Mostly is just treated with the black weevel (Cyrtobagous) but large infestations may need the help of pesticides.  The US has tried to stay away from toxicants.

  • "Salvinia Molesta could posibley be the worlds worst weed."