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Northeast Wetland Flora

Field Office Guide to Plant Species

Grassy Pondweed
Potamogeton gramineus L.

JPG -- Species Photo JPG -- Distribution Map

Family: Pondweed (Potamogetonaceae)
Flowering: July-September
Field Marks: The floating leaves of this species are elliptic to ovate and rounded at the tip, while the submersed leaves are narrowly elliptic to oblanceolate and pointed at the tip. The obovoid fruits are strongly keeled.
Habitat: Ponds, lakes, streams.
Habit: Aquatic perennial from red-spotted rootstocks.
Stems: Much branched, very slender, smooth.
Leaves: Of 2 kinds: floating leaves elliptic to ovate, rounded at the tip, tapering or rounded at the base, leathery, up to 2 1/2 inches long, up to 1 1/2 inches wide, with a stalk up to 6 inches long; submersed leaves narrowly elliptic to oblanceolate, pointed at the tip, tapering to the sessile base, finely toothed, up to 2 1/2 inches long, up to 1/3 inch wide.
Flowers: Crowded into spikes, the spikes up to 1 1/2 inches long, 1/4-1/2 inch thick; flowers sessile or very short-stalked.
Sepals: 4, green, free from each other, up to 1/8 inch long.
Petals: 0.
Stamens: 4.
Pistils: 4, free from each other, smooth.
Fruits: Achenes obovoid, prominently keeled, greenish, up to 1/8 inch long, with a short, curved beak.
Notes: Waterfowl eat the achenes.

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Page Last Modified: Saturday, 02-Feb-2013 06:15:03 EST
Menlo Park, CA [caww54]