Nesting sites for birds. A weed is a plant growing where it's not wanted. By this definition, any aquatic plant has the potential to be a weed if it hinders navigation, water movement in irrigation and flood control canals, swimming, recreational boating or fishing, or if it's abundant growth adversely affects fish populations and other wildlife. The vast majority of plant species growing in Florida waters are considered beneficial and only rarely become a problem. In the absence of natural enemies, these exotic weeds grow uncontrolled and rapidly invade new areas.
Most native plants have biological restraints that limit their abundance.
Uncontrolled growth of exotic plants disrupt the delicate ecological balance of Florida's waterways by destroying native habitat for fish and wildlife, and by destroying the biodiversity. Hydrilla, first introduced from Sri Lanka into Florida during the early 1950's, can infest and cover an entire water body in as little as three years. By 1991, hydrilla infested more than 40 percent of Florida's public lakes and rivers. A native of South America, the floating water hyacinth was first introduced into Florida during the late 1800s. It grows extremely fast, capable of doubling in area in as little as two weeks.