Holbrook Pond, Hebron

Transect Data | Water Data

     Holbrook Pond is an 83-acre waterbody located within Salmon River State Forest in Hebron, Connecticut. The pond has a maximum depth of 7.5 feet and an average depth of 4.9 feet. A trailered state boat launch and a dam are located at the southern end of the pond. The shoreline is largely surrounded by dense forest, and a short hiking trail follows much of the pond’s perimeter.

     On July 28–29, CAES OAIS conducted its second aquatic vegetation survey of Holbrook Pond since 2004. A total of 26 aquatic plant species were documented, including five invasive species. Dense vegetation limited access to the northern portion of the pond, and Transects 4, 5, and 6 could not be surveyed.

     The most abundant species observed during the survey were white water lily (Nymphaea odorata), yellow water lily (Nuphar variegata), watershield (Brasenia schreberi), and the invasive fanwort (Cabomba caroliniana). Other native species occurring at relatively high abundance included pickerelweed (Pontederia cordata), spotted pondweed (Potamogeton pulcher), purple bladderwort (Utricularia purpurea), and humped bladderwort (Utricularia gibba). Pickerelweed formed large patches primarily in the southern half of the pond, while spotted pondweed occurred in medium-sized patches near the center. Purple and humped bladderwort were restricted to shallower areas.

     Several additional species were present in one or two small patches around the pond, including primrose-willow (Ludwigia spp.), ribbon-leaf pondweed (Potamogeton epihydrus), snailseed pondweed (Potamogeton bicupulatus), rush (Juncus spp.), bur-reed (Sparganium spp.), great duckweed (Spirodela polyrhiza), arrowhead (Sagittaria spp.), watermeal (Wolffia spp.), cattail (Typha spp.), common bladderwort (Utricularia vulgaris), spikerush (Eleocharis spp.), swamp loosestrife (Decadon verticillatus), Canadian waterweed (Elodea canadensis), and spineless hornwort (Ceratophyllum echinatum).

     Among the invasive species documented, phragmites (Phragmites australis) was limited to a single small patch in the southernmost cove. The hybrid variable watermilfoil (Myriophyllum heterophyllum × laxum) has expanded since 2004, occurring in several smaller patches at the southern end of the pond, as well as one extensive patch towards the center of the pond. Although not officially listed on the CT Invasive Plant List, swollen bladderwort (Utricularia inflata) is likely a new invasive species to Connecticut. It was documented for the first time in Holbrook Pond in numerous patches in the southern half of the pond, growing in both shallow and relatively deep water. Fanwort was widespread, occurring in a large, nearly continuous patch throughout much of the pond, with little change since 2004. Northern hydrilla (Hydrilla verticillata ssp. lithuanica) was detected at the southern end of the pond, in close proximity to the boat launch. The northern hydrilla likely originated from the Connecticut River, where it was first reported in 2016. Its introduction to Holbrook Pond was likely due to boat launch activity.

 Other Holbrook Pond Surveys: 2004