Upper Guilford Lake is located in Guilford, CT. It is a 13-acre lake that does not allow motors. Boat access is by carry in only. It has a few residential homes lining its south-east side but otherwise it is surrounded by forest.

Surveyed in August of 2008, Upper Guilford Lake had eighteen plant species, none of which are invasive. The most abundant plants were white water lily (Nymphaea odorata) and watershield (Brasenia schreberi). White water lily was extremely dense in the northwest cove as well as surrounding the large island in the northern end and along the east and west shore. Watershield was extremely dense in the northeast cove and was mixed with white water lily on the west side of the island. Watershield extended occurred along most of the shoreline.

Purple bladderwort (Utricularia purpurea) was often mixed with white water lily and watershield. It was most abundant around the large north island. Yellow water lily (Nuphar variegata) was patchy along the west side to the north-east cove. Sparse populations of small pondweed (Potamogeton pusillus), pickerelweed (Pontederia cordata), snailseed pondweed (Potamogeton bicupulatus), and humped bladderwort (Utricularia gibba) were found along the southeastern corner of the lake. Flat-leaf bladderwort (Utricularia intermedia) and common bladderwort (Utricularia macrorhiza) were found in low abundance along the southeastern shoreline.