Najas flexilis

Slender Naiad

BUSHY PONDWEED

NATIVE TO MAINE

Habitat: Slender naiad is found in the submersed plant community, often growing in sand or gravel substrates.

Description: Slender naiad has fine branching stems that grow from a thin rootstalk. Leaf arrangement on a single plant may be variable, with leaves occurring in pairs, in whorls, and in crowded clumps along the stems. The size and spacing of the leaves and the overall habit of the plant are also variable, depending upon growing conditions. Some plants are tall and sparse; others short and bushy. The leaves (1 - 4 cm long, 0.2 – 1.0 mm wide) are slender, tapering to a point, and have very finely toothed leaf edges. The teeth (actually fine spines) may even be hard to see with a good hand lens. This helps to distinguish this common native plant from the invasive naiad on Maine’s watch list: European naiad. The serrations on the leaves of European naiad are visible without magnification. A second characteristic that distinguishes slender naiad from its invasive counterpart is the leaf base. Slender naiad leaves broaden gently where they meet the stem (like sloping shoulders), unlike European naiad with its squarely bulging, fringed leaf-bases. (You may need to carefully pull the leaf away from the stem to see the base.) The tiny, inconspicuous flowers, followed by slender, smooth-surfaced fruits, develop in the leaf axils.

Range: Slender naiad native to New England and northern and central U.S. Of the three Najas species occurring in Maine (slender naiad, southern naiad and thread-like naiad) slender naiad is most common by far.

Annual Cycle: Unlike most aquatic plants, slender naiad is a true annual, dying back completely in the fall and relying upon seeds to return in the spring. Vegetative reproduction may occur during the growing season. Flowers bloom through midsummer and seeds occur by mid to late summer.

Value in the Aquatic Community: The stems, leaves and seeds of slender naiad provide food to waterfowl and different marsh birds and muskrats. The branches offer food and habitat for many fish and invertebrate species.

Look Alikes: European naiad, and other species of the Najas genus including thread-like naiad and southern naiad. Slender naiad may be confused with some of the small form, fine leaved pondweeds.