Large-leaf Pondweed (Potamogeton amplifolius)

Large-leaf Pondweed (Potamogeton amplifolius) 

The Large-leaf Pondweed (Potamogeton amplifolius) is of the order Najadales and Pondweed Family (Potamogetonaceae). The order name refers to a water nymph derived from the Latin and Greek verb for "to swim.". The family and genus name is Greek for "river neighbor." The species name is Latin for "large-leaf." This plant can be several yards (meters) long. This plant is very common in French Hill Pond.

There are two types of leaves on this plant. The submerged leaves are arched, folded, broad and pointed. They are light brown and somewhat translucent. The bottom portion of the photograph above shows parts of these submerged leaves. The upper right of the photograph below shows some of the submersed leaves. These submerged leaves can grow to be 2.75 inches (7 centimeters) wide and about 2.5 times as long. These large leaves makes the identification of this plant easy. No submersed plant in Maine has larger leaves. The floating leaves are green and slightly smaller than the submersed leaves, not more than two inches (five centimeters) wide. They have prominent midveins and from 25 to 37 veins on each leaf. The tips of the floating leaves are more rounded and the floating leaves are ovate and entire. Both types of leaves are prominently veined. The lower submersed leaves are alternately arranged but the leaves at the top of the plant are arranged opposite in pairs.


Large-leaf Pondweed (Potamogeton amplifolius) in Flower 

The flower of the Large-leaf Pondweed (Potamogeton amplifolius) is a small green to brown spike just above the water on a stem as seen in the photograph above. This plant flowers from summer until fall. The fruit is an oval, dry seed with a beak and three low ridges and is a favorite food of water fowl.

The root system is rhizomic, which is a primary but slow means of propagation. It will also propagate by seed. This plant prefers areas where the water is relatively quiet.

The Large-leaf Pondweed (Potamogeton amplifolius) is similar to other pondweeds but the size of its leaves and the large, underwater leaves make it easy to identify. The Illinois Pondweed (Potamogeton illinoensi) is one of these similar pondweeds found in Maine most like the Large-leaf Pondweed but the floating leaves of the Illinois Pondweed are smaller and have a maximum of 19 veins.


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