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Egeria densa

LHPrism Status 
Tier 2 - Emerging
Moving Fresh Water
Key Characteristics 
Serrated and linear leaves seen in whorls of four to eight along the stem; small white flowers with 3 petals, bloom in late spring and in fall; 3 or more leaves per node along the stem
Impacts of this species 

Brazilian elodea forms dense mats in waterways and reduce habitat for fish, recreational value, and outcompetes native plants for sunlight; it has been seen to cause large losses to the hydroelectric companies. These plants form in dense stands and restrict water movement, trap sediment and create fluctuations of water quality. With the instability of water movement, these plants can cause interruptions of electricity generation and damage to grids and equipment. The large stands of these plants also lower recreational value of waterways and interfere with navigation, fishing, swimming and water skiing.


The Brazilian waterweed is native to much of South America, including Brazil, Argentina and Uruguay. It is figured that it was introduced into the United States and other nations through aquarium trade. It has been transported world-wide as an ornamental aquarium plant, and is cultured in a few states, such as Florida for this trade. After initial colonization, it has spread through human mechanisms and vegetative dispersal. The leaves and stems of the Brazilian waterweed generally are bright green, with a leafy appearance due to short internodes. Leaves are serrated and linear, are about 1-3cm long, up to 5mm broad, and found in whorls of four to eight. The whorls differ along the plant with the lowest leaves being opposite or in whorls of 3, and the middle and upper leaves are in whorls of 4 to 8. The stems of the plants are erect, cylindrical, simple or branched, and grow until they reach the surface of the water where they form dense mats. The 18-25mm white flowers have three petals, and float on or rise above the water's surface on thread-like hypanthiums. These plants have white or pale, unbranched slender roots are unbranched. Adventitious roots are produced from double nodes on the stem, which help these plants survive in low oxygen conditions. Brazilian waterweed is widespread throughout the Lower Hudson region, and grow best in temperate environments. It can be found in flowing or still waters, in lakes, ponds, pools, ditches, and quiet streams. It can grow, rooted, in depths of up to 20 feet, and also be found in greater depths floating on the water's surface.

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