IUCN threat status:

Least Concern (LC)

Comprehensive Description

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Description

This aquatic perennial plant consists of a submerged branching stem about 2-8' long that has both submerged and floating leaves. The branching stem is light green to pale yellow, terete to slightly compressed, and glabrous. Along its length, there are alternate submerged leaves about 1-5" long and ½-1¼" across. These submerged leaves are narrowly oblong-elliptic to lanceolate-elliptic, tapering gradually toward both their tips and their bases; their margins are smooth. The submerged leaves have 7-15 parallel veins. The petioles of the submerged leaves are ¾-5½" long. At the bases of the submerged petioles, there are linear-lanceolate stipules about 1-3½" long. The submerged leaves and stipules are green or brown and hairless; they eventually disintegrate as new leaves are produced. Toward the tips of the stems, there are alternate or opposite floating leaves about 2-6" long and ¾-1¾" across. The floating leaves are oblong-elliptic in shape, tapering to wedge-shaped or narrowly rounded bottoms and flat tips. The floating leaves have 9-17 parallel veins and smooth margins; their upper surfaces are green, hairless, and shiny. The petioles of these leaves are 1½-10" long; at the bases of these petioles, are stipules that are similar to those of the submerged leaves. From the axils of floating leaves, spikes of flowers are produced that are exerted above the surface of the water. These floral spikes are ¾-2" long, olive green to reddish brown, and cylindrical in shape. The peduncles of these flowers are 1½-6" long, hairless, and terete. The flowers are packed densely together along the sides of each spike. Each greenish flower is about 1/8" across, consisting of 4 rounded sepals that taper to narrow bases, 4 stamens, and a pistil with a single style. The blooming period can occur from late spring to late summer and lasts about 2 weeks. Afterwards, the flowers are replaced by reddish brown seeds about 3-4 mm. long and 2.5-3 mm. across. Each chunky seed has a keel on one side and a pair of parallel ridges along the opposite side; there is a short beak at its apex. The root system is fibrous and rhizomes. Colonies of plants often develop in shallow water.

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© John Hilty

Source: Illinois Wildflowers

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