Aquatic and Wetland Vascular Plants of the Northern Great Plains
55. Potamogetonaceae, the Pondweed Family
1. Potamogeton L. -- Pondweed8. Potamogeton friesii Rupr.
Stems compressed, mostly 0.5-1 mm wide, simple or branched, to 1-1.5 m long. Leaves all submersed, linear, 2.3-6.5 cm long, 1.2-3.2 mm wide, 5- to 7(9)-nerved, rounded to apiculate at the tip, the margin flat to eventually revolute, tapered to the sessile base; stipules free, white and fibrous, often shredding above, 5-20 mm long; glands present at the base of the stipules. Winter buds common, terminal or lateral, 1.5-5 cm long; inner leaves reduced, arranged into a fan-shaped structure; outer leaves 2-3 per side, apiculate to acute, indurate and corrugated at the base. Spikes cylindric, 7-16 mm long; floral whorls 2-5, 1.5-5 mm apart; peduncles slightly clavate, mostly 1.5-4(7) cm long. Fruits olive-green to brown, ovoid to obovoid, 1.8-2.5 mm long, rounded on the back. Jun--Aug. Shallow, fresh to brackish water of lakes and ponds; occasional from ND and e MT, s to n NE; (Newf. to AK, s to PA, n IN, IA, NE and UT).
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