Group 1 Species

Sago Pondweed (Potamogeton pectinatus)

Leaves, long, narrow, entire; fruits in terminal spike; stems long, thin, greenish/tan; perennial, leaves and stems senesce by late December, tubers are major food for wintering waterfowl; most widely distributed and abundant species from Last Chance to Pinehaven.

Canadian Waterweed (Elodea Canadensis)

Leaves entire, stems brittle, break easily. Can form dense mats to water surface; prefers low velocity, silty areas. Capable of persisting overwinter; highly palatable to waterfowl, vulnerable to mechanical damage, readily sprouts from fragments.

Richardson’s Pondweed (Potamogeton richardsonii)

Leaf margins entire, wavy; robust perennial; up to 4+ ft. length in east Harriman; patchy distribution, senesces by early winter; prefers silty areas with low velocity; deep rhizome system.

Water-milfoil (Myriophyllum exabescens)


Leaves pinnately divided; stems coarse, robust, pinkish; to 4+ ft. long; persists over winter; low palatability to waterfowl; may form prolific mats; high hydraulic resistance to flow.

Group 2 Species

Horned Pondweed (Zannichellia palustris)

Mat-forming annual, bright green, conspicuous “beaked” seeds in leaf axils; narrow, delicate leaves, stems numerous and threadlike, senesces by November.

Water Buttercup (Ranunculus aquatilis)

Leaves cut into many narrow divisions; usually bright green, most plants <2 ft. long; forms bushy hummocks; perennial, remains green through winter; heavily used by waterfowl; prefers fast flows; small white flowers near water surface.