top of page
Hand reaching into a waterbody showing hydrilla in the Connecticut River.


Hydrilla is an aquatic plant that has earned the title of “world’s worst invasive aquatic plant.” It is listed as a federal noxious weed and can rapidly infest rivers, streams, lakes, and ponds.


The Connecticut River hydrilla is genetically distinct from other known hydrilla strains and research on this very invasive plant is ongoing. 


CRC is collaborating with partners to develop new strategies and increase community awareness to reduce the spread of this harmful plant in our watershed. 

Hydrilla in the Connecticut River Watershed

What is Hydrilla?

Hydrilla (hydrilla verticillata) is an invasive aquatic species that was first identified in the Connecticut River in 2016 in Glastonbury, CT. Three years later, 2019 and 2020, the Connecticut Agriculture Experiment Station (CAES) surveyed the Connecticut River from Agawam, MA to the Long Island Sound, reporting at least 774 acres of hydrilla.  See CAES map of invasive plants here


In 2023, the Connecticut River strain was documented in several lakes and ponds in both Connecticut and Massachusetts, which indicates that it continues to spread. 

Hydrilla can outcompete native species and, as a result, replace habitat for sensitive species, including migratory fish. In recent years, thick mats of hydrilla have crowded out boaters, anglers and those who come to recreate on the Connecticut River. Marinas and municipalities have reported that they can no longer access boat slips and docks due to the severity of the hydrilla infestations, limiting business opportunity.   

Hydrilla Illustration Connecticut River.png
Hydrilla spread in the Connecticut River.

How Hydrilla Spreads

Hydrilla propagates through fragmentation, meaning that when it breaks apart, fragments of the plant may float downriver and re-root, creating another mat of hydrilla at a new location.


The hydrilla in the Connecticut River is different than any other species of hydrilla found. It does not have tubers on the roots of the plant, as is usual for hydrilla. Because hydrilla spreads through fragmentation, when paddlers, boaters and wildlife become entangled in hydrilla, they can spread the plant to reaches downriver.


Additionally, when boaters move from water body to waterbody, hydrilla fragments can remain in or on the vessel and be introduced to new waterbodies that way. Once in a new location, this invasive species repopulates itself rapidly and with strength.

What You Can You Do To
the Spread of Hydrilla

The first step to slowing the spread of hydrilla is to share this page with friends, family and neighbors who visit the river. When you see hydrilla in the river, avoid the infestation as much as possible so that it does not further fragment and spread. If you see hydrilla north of Agawam, MA, or in a lake or pond,  be sure to report it to CRC at the contact information below, or the appropriate state agency.   

Finally, as you travel between water bodies, it is imperative that everyone cleans, drains and then dries their boats – this applies to kayaks, canoes, jet skis, power boats and trailers. As the age old saying goes — “An ounce of prevention is worth a pound of cure.” 

Boat on the Connecticut River with two people and trees in the background.

CLEAN, DRAIN, and DRY your boat as
it travels between different water bodies 

Hydrilla spreads by fragmentation, and can easily be moved to new waters by hitching a ride on unsuspecting boats. To reduce the risk of spread, be sure to inspect and clean your boat.

How the Spread of Hydrilla is
Being Addressed

Connecticut River Conservancy has been working with municipalities, nonprofit groups, government agencies, businesses, boaters and individuals to address the threat of hydrilla.


A group of stakeholders has collaboratively written a 5 Year Management Plan to be updated on an annual basis with appropriate modifications. To learn more about the collaboration around hydrilla, watch this short documentary.


An Executive Summary of the 12-Town Environmental Review Team Report conducted by Connecticut Resource Conservation & Development can be found here.

Hand holding hydrilla in the Connecticut River.
Woman in a kayak on the river with hydrilla invasive species on the water and in a trash bag on the boat.
Hydrilla in the Connecticut River.

For questions related to CRC’s hydrilla management program, contact Rhea at rdrozdenko - at-

Hydrilla management is not currently accepting volunteers, but if you're interested in helping to remove aquatic invasive species visit our water chestnut page or contact volunteer - at -

bottom of page