To select the most appropriate management option, it is essential that the plant is correctly identified. In most situations, several species of aquatic plants are present. If one problem species is removed this might lead to the proliferation of other less desirable species.
If the plant is declared noxious you are required by law to control it. However it may be the opposite – a rare or threatened species you are lucky to have.
The most common aquatic plants can be divided into four groups depending on how and where they grow.
1. Free floating plants
These plants float on the water surface with their roots gaining nutrients directly from the water. Free floating plants include Azolla species and duckweeds including Lemna species, Wolffia species Spirodela species, salvinia (Salvinia molesta), water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes).
2. Floating attached plants
These plants are rooted into silt at the bottom of the water body, but with some or all leaves floating on the surface. Examples include waterlilies (Nymphaea species) and weed alligator weed (Alternanthera philoxeroides, which may also grow on land).
3. Submerged plants
These plants live completely under the water, although their flowers may float on the surface. They include the native ribbon weed (Vallisneria americana) and elodea (Elodea canadensis), dense waterweed (Egeria densa) and water milfoils (Myriophyllum species) as well as Cabomba (Cabomba caroliniana).
4. Emergent plants
These plants are rooted in shallow water, around the edges of water or in damp situations. Their stems and leaves appear above the water surface. Plants in this group include the rushes, such as Ludwigia peruviana, L. longifolia, Hygrophila costata, Senegal tea (Gymnocoronis spilanthoides) and horsetails (Equisetum species).