Water Chestnut Eradification Report

Aquatic Invasive Species

Photo of Water Chestnut PlantWater Chestnut Eradication Report


Water chestnut was first recorded in North America near Concord, Massachusetts in 1859. Since that time, wild populations have become established in many locations in the Northeastern United States. Water chestnut was recorded for the first time in the Bird River in Baltimore County in 1955. The Maryland Departments of Game and Inland Fish and Tidewater Fisheries used mechanical removal and chemicals (the herbicide 2,4-D) to control the population.

In 1964, water chestnut reappeared in the Bird River and an additional 100 acres were discovered in the Sassafras River in Kent County. Thirty acres were mechanically removed from the Sassafras River in 1964. A combination of removal techniques were used once again in 1965, when 200 acres were eradicated on the Sassafras.

The harvesting efforts were believed to have been successful, and no plants had been reported until the summer of 1997. A call from a landowner on the Bird River about an unusual plant led to the discovery of a small population of water chestnut in a cove just upriver from Railroad Creek. From the summer of 1997 to the summer of 1998, these plants expanded from 3 acres to approximately 30 acres, and reports were also received of water chestnut growing in Lloyds Creek of the Sassafras River. Both populations were in the same locations from which water chestnut had been harvested in the 1960's, suggesting that this was a resurgence of the same population of plants.

The Maryland Department of Natural Resources attempted to eradicate water chestnut from the Bird River, Harford County and the Sassafras River, Kent County during the summer of 1999. The population in the Bird River had spread from approximately 50 plants in the summer of 1997 (based on conversations with local landowners) to over three acres in 1998. By this time, the three acre area was so heavily covered with plants that the water beneath the plants was barely visible. The Sassafras population was believed to be slightly larger, but determining the exact quantity was not possible. Based on conversations with aquatic plant control experts from around the country, it was decided that application of the herbicide 2,4-D would be a safe and effective control technique. Despite this advice, public and state concern over the application of an herbicide to Chesapeake Bay waters lead DNR to save herbicide application as a last resort in the event that other techniques didn’t work. It was decided to launch a large mechanical and hand removal effort.

Water Chestnut Management Timeline

Water Chestnut Harvest results (1999-2012) 


  • Mechanical harvesting using an aquatic plant harvesting boat took place on 14, 15 and 16 of June on the Sassafras, and June 18 on the Bird, removing an estimated 260,000 pounds of water chestnut.

  • A follow-up hand harvesting effort took place in July to clean up the remaining plants.

  • All harvested plants were composted in the water using floating cages designed specifically for the project.


  • A combination approach was used, with mechanical harvesting by boat followed by hand removal by volunteers. Approximately 30 volunteers manually removed plants from the Sassafras River and 40 volunteers manually removed plants from the Bird River.

  • Less than 1000 pounds of plants were discovered and removed from rivers in 2000, indicating that mechanical and hand removal efforts were successfully reducing the total number of plants.


  • In the Sassafras River, about 2 acres of Lloyds Creek and 3 acres of Shallcross Creek contained scattered plants. The harvester cut and collected the majority of plants over the course of two days.

  • Groups of volunteers then combed the river for additional plants in late June removed several more bushels.

  • In the Bird River, the harvester worked for one day, cutting less than 150 pounds of plants from a small tributary upriver of Railroad Creek. Volunteers finished the job on June 15th, with only a handful of additional plants being collected.


  • Efforts once again took place on both the Bird and the Sassafras River in mid to late June, using approximately 80 volunteers.

  • Not enough plants were present at any of these locations to justify using a mechanical harvester- a significant milestone for the overall eradication effort.

  • The total volume of plants harvested declined once again, with only a few bushels of plants harvested from the Bird River, and about 200 pounds of plants from the Sassafras.

  • The combination of mechanical and hand removal of plants from 1999-2002 has proven to be so successful that there has been no need to resort to herbicides to control this pest. It is likely, however, that continued efforts at water chestnut harvesting will be needed for several more years before we are able to truly claim that the water chestnut infestation is a thing of the past.

2003 - 2007

  • Control efforts were performed on both rivers using personal watercraft, DNR work boats, as well as canoes and kayaks.

  • Beginning mid June, DNR personnel surveyed all shoreline areas in the vicinity of the original populations and for several miles along the shoreline both upriver and downriver. In each year, a few hundred plants were found in each river in generally the same areas as the first several years.

  • In 2004, a substantial additional population of plants was discovered in a small pond off the eastern shore of Woodland Creek not easily visible from the river. Approximately 600 pounds of water chestnut were harvested from this pond and the cove into which it outflows. In 2005, no plants were found in this pond, but another pond was found across the river that also contained several hundred pounds of water chestnut.


  • The Sassafras River Association joined the effort to control water chestnut, and assisted with the collection in June.

  • A private landowner off of Woodland Creek contacted DNR to request a biologist survey his sediment pond. Approximately 2 acres of the pond were covered with water chestnut, and after an unsuccessful hand removal effort, the pond level was lowered significantly over the winter.

  • The pond was treated in July 2008 with Clearcast, and there is very little water chestnut left in the pond in the summer of 2009. An outreach effort was conducted though the Sassafras River Association to find any private landowners that may have water chestnut infestations on their property.


  • Removal efforts continued on the on both the Bird and Sassafras Rivers.

  • Approximately 25 bushels of plants were removed from a small, unnamed creek adjacent to Railroad Creek and Taylor Creek (adjacent to Mariner Point Park). No plants were found in Day’s Cove.

  • DNR biologists worked with the Sassafras Riverkeeper and volunteers from the Sassafras River Association to remove 60 bushels of water chestnut from Turners Creek, Dyer Creek, Woodland Creek, Island Creek and a small cove behind Pond’s Bar adjacent to the Sassafras Natural Resources Management Area. The majority of the plants were collected from Turners Creek.


  • A record low two bushels were harvested on the Sassafras River, with most of them found in Lloyds and Woodland Creeks.

  • On the Bird River, 10 bushels were harvested in Days Cove. GPS coordinates are used to mark infestations, and they indicate that infestations are found in the same general areas year to year.


  • On the Sassafras River, a sharp increase in population was observed, with 220 bushels being collected in Lloyds Creek and 120 bushels collected in Turners Creek.

  • On the Bird River, 25 bushels were found in Day Cove, which was more than double the previous year.

  • After a year of record lows on both rivers, it became obvious the seed bank that repopulates these areas is fairly substantial.


  • After a year with substantial increases in both rivers, 2011 yielded 50 bushels on the Sassafras 40 bushels on the Bird River.

  • The combination of mechanical and hand removal of plants from 1999-2010 has proven to be so successful that there has been no need to use herbicides. It is likely, however, that continued efforts at water chestnut harvesting will be needed indefinitely to keep the population in check and to prevent further spread. Funding is actively sought to allow an expansion of the control effort.


  • The Sassafras River had a sharp decrease in water chestnut in Lloyds and Turners Creek, but an increase in Woodland, Island and Dyer Creeks. Crews from DNR and the Sassafras Riverkeeper removed 30 bushels in the Sassafras, but were forced to cut the harvest short due to Mycrocystis blooms starting in June.

  • On the Bird River, DNR field staff and interns removed 12 bushels of water chestnut, a sharp decrease from the year before.

  • DNR will continue to work with the Sassafras Riverkeeper and local volunteer groups to keep water chestnut under control on the Bird and Sassafras Rivers. 

2012 Water Chestnut Infestations

Photo of Sassafras River (East) Water Chestnut Infestation Photo of Sassafras River (West) Water Chestnut Infestation Photo of Bird River Water Chestnut Infestation

Sassafras River (East)

Sassafras River (West)

Bird River