Robbins Pondweed (Potamogeton robbinsii)
A large field of Robbins Pondweed was found by Brad Gaudreault around the southern edges of the Thorne Islands in Zone 5. It was deep enough in the water that Cliff also dove to help identify it. A sample was sent to Amy Smagula for confirmation. A fragment was also collected by Maria Gross in Zone 7.
Leaves are alternately attached on opposite sides of the stem, ascending to spreading and often arching, usually closely spaced but may be more widely spaced on flowering stems.
Blades are firm and somewhat stiff, dark green to reddish, lance-linear, ¾ to 2¾ inches long, 1/8 to 1/3 inch wide, pointed at the tip and minutely toothed around the edges, at least near the tip. The midvein is conspicuous yellow, flanked by 20 to 60 lateral veins, about 5 of which are prominent and the rest faint.
Stems are round, without spots, few-branched on the lower plant, branching frequently in the upper plant when flowering. Colonies are often formed from creeping rhizomes. (Excerpted from MinnesotaWildflowers.info/aquatic/robbins-pondweed).