You Can Help Prevent the Spread of Invasive Plants: What Every Plant Enthusiast Needs To Know

Characteristics of Invasives

Most invasive species have certain traits that make them successful in habitats that they invade. Invasive aquatic and wetland plants generally:

• tolerate a wide range of environmental conditions including soil and water acidity, water and air temperature, water salinity, water level fluctuations, and dissolved oxygen;
• reproduce early, often, in large numbers, and in multiple ways (e.g., by fragmentation, seeds, and rhizomes);
• grow rapidly;
• resist management control efforts.

Vectors of Spread

Mother Nature
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.

Plant Enthusiasts
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
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.

Before building & choosing plants for your water garden

Build your water garden away from natural waterways

• When planning your water garden, choose a site that is isolated from any potential flooding situations (i.e., a lowland area adjacent to a river is likely to flood). Remember, use of invasive plants in a water garden that is near a lake, river, stream, or even a retention basin could increase the risk for spread of those species.

Familiarize yourself with invasive plants of regional and national concern

• The Sea Grant Most Wanted; your own state's lists and U.S. Federal Noxious Weed List are good starting points. Your state natural resource agency also is a valuable information resource.

Consider using regionally native or non-invasive exotic plants

• There are many non-invasive plants that can be used in place of an invasive species to achieve the same effect whether balancing pH, providing vertical interest, or adding a particular color.

Use invasive plants only outside of their hardiness zone

• Those plants whose temperature and precipitation requirements are far outside the limits of your agricultural zone are less likely to become invasive if they escape to natural waterways.

When buying aquatic plants

Choose a reputable nursery (whether you shop at a store, through a catalogue, or via the Internet).

• Ask if the vendor is aware of what species are regionally and federally restricted.
• Verify that the plant identifications and their scientific names (i.e., genus and species) are correct. Common names are sometimes used interchangeably for several different species, so you could accidentally buy an invasive species labeled with a harmless pseudonym.

Ensure that your purchases are free of any hitchhikers.

• Rinse plants in a bucket of tap water until they are clean. The dirtier the plant, the more likely it is to have hitchhikers. Be on the lookout for snails and plant fragments. Use a light colored bucket to help you see the hitchhikers.
• If it seems likely that your plant has hitchhikers, use a chlorine dip. Dip the plant in a 10% chlorine solution, swish it around, and then shake it off. After 30 seconds, rinse the plant with tap water. This method will not harm emergent plants such as Sagittaria spp. (arrowhead), but is not recommended for submerged plants such as Vallisneria americana (wild celery).

Disposing of aquatic plants

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.

• Completely dry or freeze the plants, and then add them to the household garbage that does not get composted. Composting should be avoided because many seeds can withstand drying and freezing. An alternative method of disposal is to burn the plants if backyard burning or trash incineration is an option.

Expanding your efforts

• Inform others about the problems of invasive aquatic plants and the methods to prevent their spread.
• Report sightings of invasive plants in natural waterways to your local or state agricultural agent, extension office, or natural resource management agency.
• Volunteer to help remove invasive plants from vulnerable natural areas. Call your state natural resource agency about volunteer opportunities.

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