Emersed or submersed perennial with smooth stems, trailing on ground and forming dense mats.  Grows in water or very wet soils.

Submersed perennial with rhizones, stem branched and somewhat flattened.  Leaves reddish-green, alternate, oblong, with finely toothed edges.  In habits ponds, lakes, and streams.

Several species found in US, often found growing together.  Small floating herb, which grows rapidly to cover surface of still waters.

Submersed prennial, rooting in mud.  Stems branched, usually purple, to 3 meters long.  Leaves in whorls of 3-4, pinnately divided into 6-16 pairs of leaflets.  Flowers unisexual, borne in whorls.  Infests lakes, ponds, streams, and estuaries, fresh and brackish water, up to 5 m in depth.

Fanwort or Carolina watershield is a submerged aquatic perennial that has become a popular ornamental plant for water gardens and aquariums. Its bright green feathery foliage is quite attractive.   Branching stems to 6’ long are densely clad with opposite, fan-shaped leaves that are finely divided into numerous filiform segments. Small linear-oblong peltate floating leaves are sparsely located at the branch ends and rest on the water surface in a manner somewhat reminiscent of tiny water lilies.  White-petaled flowers (1/2” across) rise slightly above the water surface on long stems growing from the leaf axils.

Arundo donax grows in the southern half of the contiguous United States, being found along ditches, culverts, and roadsides where water accumulates. It has been used extensively as a windbreak, and planted for erosion control on wet dunes. It is also grown for the ornamental value of its tall, leafy culms and large panicles, but its tendency to spread is sometimes a disadvantage.

Free-floating fern, with pair of floating leaves up to 4 cm long.  Leaf surfaces have rows of papilla branching into hairs.  Inhabits quiet waters such as lakes, ponds, oxbows, swamps, and marshes.

Submersed perennial with branched stems to 1 m long, and forming turions and tubers.  Leaves whorled to 15 mm long by 4 mm broad, toothed, red-viened, spinulose on the lower suface.  Infests most water habitats, forming dense mats.

Lyngbya is one of the groups of cyanobacteria that are of special concern. This long, hair-like organism is a filamentous alga that can form large benthic (on the bottom) and surface mats (blooms). Lyngbya normally grows in dense mats at the bottoms of nutrient enriched lakes and spring fed systems. These mats produce gasses during photosynthesis that often causes the mats to rise to the surface. At the surface, winds pile the algal mats against shorelines or in navigation channels; these mats can be several acres in size. Lyngbya, is one of the cyanobacteria that is known to release toxins into the water. These three toxins, debromoaplysiatoxin, aplysiatoxin and lyngbyatoxin have been found to be a major cause of dermatitis.

Erect, tall perennial from stout, creeping rhizones.  Stems to 4 m tall.  Leaves flat, smooth on the surface to 5 cm broad.  Large inflorescence (15-40 cm), yellow to purple, blooming from July to September.  Abundant in marshy habitats, often forming extensive colonies.

Erect herbaceous perennial with showy purple flowers.  Prolific seed production aids in spread of the plant.  In winter, dies back to the root crown, and regrows in spring.  Colonizes moist soil to emergent shallow water areas, may even grow in moist upland areas

Fast-growing, floating aquatic plant that can grow up to 16 feet long, forming dense mats. Submerged leaves are feather-like, and emergent leaves are triangular and toothed.  Seeds are covered with sharp, tough spines, and can cause foot injury.

Free- floating plant that is capable of forming dense mats on water surfaces.  Thick leaves closely resembling a head of lettuce.

Floating perennial, rooting at the nodes.  Leaves elliptical to round, up to 20 cm long by 15 cm broad.  Blue-purple flowers borne in racemes, 4-6 cm long.  Infests streams, ponds, ditches, backwater areas.