Wetland Plants and Plant Communities of Minnesota and Wisconsin

ILLINOIS PONDWEED

(Potamogeton illinoensis Morong)

PONDWEED FAMILY (Potamogetonaceae)

IND. STATUS: OBL

FIELD CHARACTERISTICS: An aquatic, perennial herb. Submerged leaves are sessile or on petioles not over 2 cm. long. The submerged leaves are 0.83.2(5) cm. wide with (7)9-19 nerves, and have a pointed tip that can be up to 4(5) mm. long. Floating leaves (if present) have blades 1.7-3(3.5)cm. wide with petioles that are shorter than the blades. Flowers are on emerged spikes. Fruits are 3-4 mm. long and somewhat sharply keeled.

ECOLOGICAL NOTES: Illinois pondweed is found in lakes and rivers, especially calcareous waters, in depths to 15 feet.

SOURCE: Fernald (1970); and Voss (1972).

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