Lake Quonnipaug supports a diverse community of aquatic plants, with 21 submerged species, three floating-leaved species and one emergent recorded during a June 2004 survey. Four of the species were invasive. The most abundant species was Robbins pondweed (Potamogeton robbinsii), which covered the bottom in the middle of the lake, in water up to 12 feet deep. The most species-rich areas of the lake, where no single species was dominant, were the shallow waters of the lake’s north end and a narrow finger at the southern end of the lake.
