Robbin’s pondweed

Pond Weeds

Potamogeton robbinsii:

Robbin’s pondweed

Potamogeton robbinsii Oakes: Flatleaf pondweed, fern-leaf pondweed, Robbin's pondweed. Potamogetonaceae (pondweed family). 

Native perennial. Submersed plant with a single leaf type and no floating leaves; grows up to 10 ft (3 m) but remains low in the water-column, stems often not reaching the surface until they flower. Individual leaves are rigid, linear, 1.2 - 4.75 in (3 - 12 cm) long, narrowing to a point at the tips and becoming narrower towards their bases where they meet the stem. Lower on the stem the leaves are spaced farther apart but near the top the stiff dark-green leaves emerge closer together, flattened in a single plane; they resemble fern fronds or palm leaves. They may emerge so close together that they look like stiff ribs of a fan. Stipules are pointed, up to 1.2 in (3 cm) long, and clasp the stem at their base; they often are worn away so that only the veins remain. Flower spikes are borne on slender, 1 in (2.5 cm), stalks that are stiffer and flatter than those of other pondweeds.