Florida has many species of aquatic plants, with some native to the state and others establishing themselves within its boundaries from other places. The recognition of the distinct species of aquatic plants in Florida requires you to observe a number of their characteristics. These include such features as their habitat, leaves and flowers, as well as noting the shapes and sizes of the plants you encounter in and along the state's waters.
Where you find an aquatic plant can aid your identification process. For example, species such as water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) will float on the top of ponds, lakes and quiet rivers. Others, such as eelgrass (Vallisneria americana), will be below the surface of the water. A number of aquatic species occur along the shorelines or growing out of the water close to shore. These include cattails (Typha) and arrowhead (Sagittaria latifolia).
The shape of aquatic plants in Florida can help you figure out what they are. This is particularly true of the floating aquatics. Spatterdock (Nuphar advena) features large heart-shaped leaves, while white water lilies (Nymphaea odorata) have a rounded leaf on the surface with what appears to be a large notch taken out. The leaf shape of some emergent aquatic plants also is important to recognizing them. Alligator weed (Alternanthera philoxeroides), for instance, has a long elliptical leaf.
Measuring the length and width of the leaves and/or the entire aquatic plant is helpful when trying to identify species. Cattails may grow to be as tall as 9 feet, notes the Florida Fish and Wildlife Conservation Commission. Sawgrass (Cladium jamaicense) reaches a similar height, but possesses leaves that can be 4 feet long and ½ inch wide. The feathery leaves of coontail (Ceratophyllum demersum) are only 1 inch long, while the floating American lotus (Nelumbo lutea) leaf may be 3 feet wide.
Many of Florida's aquatic plants produce flowers, some of which are quite distinctive. Such is the case with the water hyacinth, known for its attractive brilliant purple flowers rising on a stalk over the plant. Water lilies, water lotus and spatterdock all have distinguishing blooms. Knotweeds (Polygonum), an emergent plant, will produce a spike of pink and white flowers that occur on the top of the plant.
Observing the leaf arrangement on submerged Florida aquatic plants will give you a good idea of the type of plant growing under the water. Some have a whorled pattern of leaves, growing around the stems, such as southern naiad (Najas guadalupensis) and hydrilla (Hydrilla verticillata). Others will possess complicated-looking branched stems, such as bladderwort (Utricularia). Still others, including a species known as fanwort (Cabomba), have leaves that grow opposite one another on the plant's stem.