The aquatic plant community in the Charles River watershed is unfortunately dominated by invasive plants. Polluted stormwater runoff carrying nutrient pollution allows these plants to grow out of control. Here are a few of the most common invasive aquatic plants you’ll encounter along the Charles.
Eurasian water milfoil (Myriophyllum spicatum)
Milfoils are characterized by feather-like “leaves” that have 11 stick-like leaflets on either side. The leaves are arranged in whorls around the plant’s stem, with 3-6 leaves in each whorl. If you encounter it, do not attempt to pull the plant out. Clean your boat to ensure that fragments are removed and dispose of the plants away from water bodies.
Fanwort (Cabomba caroliniana)
Source: Shoal Creek Conservancy
Like milfoils, fanwort also has stick-like leaflets, but instead of being arranged in an elongated feather shape, its leaflets are arranged in a rounded fan shape. Leaves are arranged in pairs along the stems of fanwort plants. Fanwort flowers in late summer. Flowering plants produce small, full leaves and white flowers at the water’s surface. If you encounter it, do not attempt to pull the plant out. Clean your boat to ensure that fragments are removed and dispose of the plants away from water bodies.
Curly-leaved pondweed (Potamogeton crispus)
Source: Leslie J. Mehrhoff, University of Connecticut, www.bugwood.org | CC BY 3.0
Unlike milfoils and fanwort, the leaves of pondweeds are not divided into leaflets. Curly-leaved pondweed has long, narrow leaves that have toothed edges, which creates a wavy appearance. If you encounter it, do not attempt to pull the plant out. Clean your boat to ensure that fragments are removed and dispose of the plants away from water bodies.
Water chestnut (Trapa natans)
The most prominent part of a water chestnut plant is the rosette of triangular, toothed leaves that float on the water’s surface. Feather-like leaves may also be present underwater. In late summer, water chestnut plants release spiked seeds that will produce new plants in late spring the following year. If you see water chestnut plants in the Charles River Lower Basin please contact us.
Eurasian water milfoil, fanwort, and curly-leaved pondweed reproduce vegetatively, which means that if a piece of one of these plants is broken off, it can form roots and grow a new plant. This makes it especially important to clean your boat motor. If any of these plants have become entangled on your boat motor, you should remove the fragments from the motor and compost them in an upland area away from any nearby waterways or dispose of them in a black trash bag. Do not throw the plants back into the water, or you will make the invasion worse!