Most invasive species have certain traits that make them successful in habitats that they invade. Invasive aquatic and wetland plants generally:
Invasive plants are generally spread to natural waterways accidentally. These unintentional introductions are more likely if a water garden or a retention basin containing invasive plants is built near a natural body of water. The natural waterway may flood into the artificial pond and carry away the contents, or the pond may flood and have its contents swept away into the natural waterway. In addition, seeds and plant fragments of invasive plants can be spread by wind or by traveling wildlife.
Water gardeners and aquarium hobbyists can unintentionally spread potentially harmful plants when they 1) share specimens among friends, neighbors, and gardening and aquarium clubs, or 2) dispose of aquatic plants by releasing them into a natural waterway. Invasive plants are also spread when gardeners moving to warmer climates take plants with them that would otherwise have been controlled in colder climates (i.e., killed during winter). Instead, these plants thrive and become invasive in their new warmer habitat. Some plant enthusiasts even sneak novel plants into the country illegally. By introducing these exotic plants, they run the risk of causing great harm. (Note: Any plants that are brought into the country should be declared to quarantine officials.)
Retail outlets may also contribute to the spread of invasive species. These outlets can sell invasive plants unless the state or federal governments specifically prohibit their sale. In some cases, even prohibited plants may end up being sold if retailers are 1) unaware of the restrictions, or 2) unfamiliar with a plant's scientific name and only know it by a non-invasive alias. Retailers may also sell plants (or use packing materials!) with "hitchhiking" plant fragments or invertebrates (small animals) that may themselves be invasive.
Build your water garden away from natural waterways
Familiarize yourself with invasive plants of regional and national concern
Consider using regionally native or non-invasive exotic plants
Use invasive plants only outside of their hardiness zone
Choose a reputable nursery (whether you shop at a store, through a catalogue, or via the Internet).
Ensure that your purchases are free of any hitchhikers.
Dispose of aquatic plants if they are 1) in a habitat where they could spread into nearby waterways, or 2) in a water garden that is being emptied for the winter.
The information presented was extracted from the brochure, "Invasive Aquatic Plants: What Every Plant Enthusiast Needs to Know," written by Patrice M. Charlebois and Kristin TePas of the Illinois/Indiana Sea Grant of the University of Illinois.
A joint project of Sea Grant and other offices of the University of Connecticut, University of Florida, University of Minnesota, University of Illinois, North Carolina State University and Purdue University