Lake Quonnipaug, Guilford - 2004
2004 Aquatic Plant Survey Map of Lake Quonnipaug

Transect Data | Water Data

Residents of the 99-acre Lake Quonnipaug have been concerned by the abundance of plants in this area, and both mechanical and herbicide treatments have been attempted. Many homes have been built on the eastern side of the lake, and Route 77 runs along the lake’s west side. A town beach occurs on the west side as well, and the state maintains a boat launch at the lake’s north end.        

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.           

The most abundant species at the lake’s northern end were curlyleaf pondweed (Potamogeton crispus), white water lily (Nymphaea odorata), and yellow water lily (Nuphar variegata).  Individual plants to small patches of Eurasian watermilfoil (Myriophyllum spicatum), large-leaf pondweed (Potamogeton amplifolius), Robbins' pondweed, and western waterweed (Elodea nuttallii) also were found in the area.           

The western side of the main body of the lake was dominated by Robbins' pondweed. Individual plants or small patches of watershield (Brasenia schreberi), white water lily, yellow water lily, Eurasian watermilfoil, and large-leaf pondweed were found. Several small, shallow coves on the east side of the lake supported more abundant populations of several aquatic plants. Growing with the dominant Robbins' pondweed were white water lily, yellow water lily, Eurasian watermilfoil, large-leaf pondweed, curlyleaf pondweed, watershield, and western waterweed.           

Two large areas in the middle of the lake were too deep to support aquatic plants. The lake has a maximum depth of 45 feet and a mean depth of 18 feet. In a large, shallow, mid-lake area, large-leaf pondweed grew abundantly with Eurasian watermilfoil and some curlyleaf pondweed.           

Many species were recorded in the narrow southern cove off the main body of the lake. White water lily and yellow water lily were the most abundant floating-leaved species, and Eurasian watermilfoil and coontail (Ceratophyllum demersum) were the most abundant submersed species. The channel also contained individual plants or patches of a large number of other species.

Species recorded in our 2004 survey of Lake Quonnipaug.
Scientific Names
*Invasive Species
Common bladderwort Fanwort* Large-Leaf pondweed Slender naiad Water stargrass
Coontail Flat-Stemmed pondweed Oakes' pondweed Small pondweed Watershield
Curlyleaf pondweed* Floating-Leaf pondweed Purple bladderwort Spiral pondweed Western waterweed
Eelgrass Grassy arrowhead Ribbon-Leaf pondweed Variable pondweed White water lily
Eurasian watermilfoil* Humped bladderwort Robbins' pondweed Variable-Leaf watermilfoil* Yellow water lily

Other Lake Quonnipaug Surveys: 2020, 2015, 2010