Brazilian water weed
- This plant has a Plant Risk Evaluator rating of No PRE Rating
- This plant has been rated High by the California Invasive Plant Council
Egeria densa is an aquatic perennial in the waterweed family with stems up to 15 ft long that are frequently branched. It is native to Argentina, Brazil, and Uruguay, and has been distributed via the aquarium trade to many parts of the world. When it was brought to California is unknown. It ends up in waterways when people dispose of the plant in waterways.
Once naturalized it can spread along existing water courses into new habitats without help from humans. Stem fragments two nodes long or more frequently break off and float away from the parent plant. In California it has spread only by dispersal of pieces of the plants and by rhizomes since only the male plant has become established.
Its dense underwater growth retards water flow, interferes with irrigation projects, hydroelectric utilities, and urban water supplies. It may also slow water traffic and interfere with boating, swimming and fishing. Egeria densa reduces the abundance and diversity of native plant seeds on lake bottoms.
In California it occurs mostly in the Sierra Nevada and Sacramento Valley, including in the Sacramento - San Joaquin Delta. CalWeedMapper shows its current distribution in California outside of cultivation.
Why is this plant not included on the invasive plant list?
Brazilian waterweed was considered for addition to the list in 2014 and included in the 2014 nursery survey, during which it was found at 0.4% of nurseries. It is not commonly sold enough to add to the list and its too late for addition to the PlantRight list for its addition to have an impact on its distribution in California.
For more information about this plant, please see the following resources: