Naiads (Water Nymphs; Waterweeds)
Naiads are slender, narrow-leaved plants that grow completely under water and are rooted to the bottom. The leaves are slender, have finely toothed edges, occur in pairs or whorls, with each leaf base swollen to form a sheath around the stem. There are tiny, greenish flowers at the leaf bases.
Four species of naiads have been recorded in Missouri. The most common is southern naiad (N. guadalupensis), a native species that forms large mats and is sometimes encrusted with lime. Brittle naiad (N. minor), an introduced species, is expanding its range and is expected to become more widespread. Its leaves curve backward during the growing season and have teeth along the edge that are visible without magnification.
Similar species: Several other plants, including some of the narrow-leaved pondweeds. Naiads, however, never have broad, floating leaves or conspicuous flowers or seed heads.