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Potamogeton spirillus


Northern snail-seed pondweed in-situ
Northern snail-seed pondweed in-situ

Habitat: Northern snail-seed pondweed grows in the submersed plant community. It is found in relatively shallow, quiet portions of lakes, ponds and slow moving streams, and prefers neutral to acidic water.

Description: Northern snail-seed pondweed produces two distinct leaf types: submersed leaves and floating leaves. Both leaf types are entire. Compact clumps of slender, often profusely branching stems emerge from delicate roots and rhizomes. Stems are slightly compressed in cross-section. Submersed leaves are narrow and strap-shaped (1 to 8 cm long, and 0.5 to 2 mm wide), rounded at the tip, and often slightly curled. They are attached directly to the stems (no petioles) and are alternately arranged in spirals along the stem. Light-colored, translucent bands of air-filled cells (called lacunae) occur along both sides of the midvein. Stipules are fused to submersed leaves for more than half of their length (often only the tips of the stipules are free). Floating leaves, when present, occur at the waters surface on slender petioles (0.5 to 2.5 cm long). The leaves are small (0.7 to 3.5 cm long) and oval. Flowers are minute and inconspicuous. Tiny fruits are generally produced in clusters, and occur either in the leaf axils or dangling loosely on the ends of thread-like stalks. Fruits look like flattened, faintly-spiraled disks. A series of blunt points may occur along a portion of the disk edge. (A hand lens is helpful when observing lacunae, stipules and fruits.) Northern snail-seed pondweed is often light green to golden in color.

Northern snail-seed pondweed Range Map
U.S. range map of Northern snail-seed pondweed

U.S. Range: Northern snail-seed pondweed is native to Maine and New England, occurring throughout much of the northeast and north central United States.

Northern snail-seed pondweed seeds
Northern snail-seed pondweed disk-like fruits

Annual Cycle: Northern snail-seed pondweed is an aquatic perennial that propagate by creeping rhizomes and seeds. Flowers occur in the spring and fruits mature by mid-summer. Plants die back to their rhizomes as winter sets in, depositing seeds on the sediments. New growth sprouts from the rhizomes and seeds as the water begins to warm in the spring.

Value to the Aquatic Community: Northern snail-seed pondweed is grazed upon by fish, waterfowl and invertebrates. The compact, bushy plants provide shelter for fish fry.

Look Alikes: Submersed leaves of northern snail-seed pondweed may be confused with some other narrow-leaved species of the Potamogeton genus, European naiad, Slender naiad, threadlike naiad, and some Stoneworts.

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Northen snail-seed pondweed in-situ Northen snail-seed pondweed seed Northen snail-seed pondweed range map Northen snail-seed pondweed illustration

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