Narrowleaf Pondweed

Potamogeton strictifolius is a relatively uncommon species found in alkaline waters. Fairly rigid leaves of the species make floating onto paper unnecessary in the collecting process. The leaves have a tendency to become revolute during the growing season. The species superficially resembles several other species of linear-leaved pondweeds. Consequently, many specimens of this species have been misidentified as other species and vice versa. Thus, literature records are often suspect.

One hybrid, Potamogeton strictifolius ´ P. zosteriformis (= P. ´ haynesii Hellquist & G. E. Crow), has been described.

Rhizomes absent. Cauline stems terete, without spots, 27--95 cm; glands white, green, greenish brown, or gold, to 0.3 mm diam. Turions terminal or lateral, common, 2.5--4.8 cm ´ 0.8--2.2 mm, soft; leaves ± 2-ranked, flattened with outer and inner leaves in same plane; outer leaves 3--4 per side, base not corrugate, or rarely corrugate, apex acute; inner leaves undifferentiated. Leaves submersed, ± spirally arranged, rigid, sessile; stipules disintegrating, inconspicuous, connate, free from blade, white, not ligulate, 0.6--1.6 cm, fibrous, shredding at tip, apex obtuse; blade green to olive-green, linear, not arcuate, 1.2--6.3 cm ´ 0.6--2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to nearly bristle-tipped, rarely obtuse to apiculate, lacunae absent; veins 3--5(--7). Inflorescences unbranched, emersed; peduncles not dimorphic, terminal, erect, rarely recurved, cylindric, rarely slightly clavate, 1--4.5 cm; spike not dimorphic, cylindric, 0.6--1.3 cm. Fruits sessile, green-brown, ovoid, turgid, not abaxially or laterally keeled, 1.9--2.1 ´ 1.3--1.8 mm; beak erect, 0.5--0.8 mm; sides without basal tubercles; embryo with 1 full spiral. 2n = 26.

Alta., Man., N.B., Ont., Que., Sask., Yukon; Conn., Ill., Ind., Maine, Mass., Mich., Minn., Nebr., N.Y., N.Dak., Ohio, Pa., S.Dak., Utah, Vta., Vat., Wis., Wyo.

Flowering and fruiting summer--fall.

Alkaline waters of lakes and slow-moving streams; 50--2000m.

Potamogeton strictifolius A. Bennett var. rutiloides Fernald