Najas flexilis

Slender Naiad

Slender Naiad, Photo courtesy of Wisconsin State Herbarium and Robert W. Freckmann
Slender Naiad
Photo courtesy of Wisconsin State Herbarium
and Robert W. Freckmann

Flora, fauna, earth, and sky...
The natural history of the northwoods


  • Najas, from the Greek, naias (Naias), "Naiad, river-nymph, spring-nymph"
  • flexilis, from the Latin, "flexible, pliable, bendable"
  • Common name from the Naiads, the freshwater nymphs of Greek mythology
  • Other common names include: Nodding Waternymph, Northern Water Nymph, Wavy Waternymph, Liden Najade (Dan), Notkeanäkinruoho (Fin), Aibhneag (Gaelic), Biegsames Nixenkraut (Ger), Mjukt havfrugras (Nor), Sjönajas, Sjösärv (Swe)


  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Liliopsida, the Monocotyledons
      • Subclass Alismatidae
        • Order Najadales
          • Family Najadaceae, the Water Naiads
            • Genus Najas, the Water Naiads
  • Taxonomic Serial Number: 38996
  • Also known as Caulinia flexilis, Fluvialis flexilis, Najas caespitosa, Najas canadensis


  • An annual aquatic herb.
  • Leaves pale green, simple, linear to very narrowly lanceolate, opposite, sessile, abruptly broadened at the base to sheath the stem. Densely clustered at stem tips, leaves are ¼"-1¼" long, up to 1/16" wide, with edges faintly to coarsely toothed. (Each leaf typically has 20-40 minute spinules on each side of the leaf). Leaves often have enrolled margins and a recurved tip, gradually tapering to the base.
  • Stem submerged, smooth, wavy, freely branched, 2"-12" long, anchored by roots. Terminal nodes crowded; internodes dark green to light yellow to reddish.
  • Roots fibrous; rhizomes absent.
  • Flowers imperfect; plants monoecious, with male and female blooms borne separately in the axils of the leaves but on the same plant. Flowers minute, imperfect, solitary, and sessile, enclosed by the sheathing leaf bases.
  • Male Flower consists of a single anther enclosed in a membranous envelope (spathe), this in turn surrounded by a firmer, entire to 4-lobed, perianthlike structure.
    • Sepals 0
    • Petals 0
    • Stamens 1
  • Female Flower comprised of a single, 1-ovuled pistil.
    • Sepals 0
    • Petals 0
    • Stigmas 2-4, style usually elongate and persistent.
    • Ovary superior (within blossom)
  • Fruit an achene, olive-green to reddish, the beak 1 mm or more long, the pericarp thin and easily removed to expose the single seed.
  • Seed ellipsoid, slender, seed coat shiny, up to 1/8" long, 1/3 as thick as long, marked with 30-40 longitudinal rows of obscure pits across the middle, covered by a yellow to purplish coat.


  • A slender, elongated, rooted aquatic plant, seldom found in water less than 3' deep.
  • Distinguished from similar species by:
    • slender, opposite leaves which clasp the stem
    • elongated, wavy form, rooted to the bottom


  • Newfoundland and Quebec to SE Manitoba, south to Maryland, Indiana, Iowa, and Nebraska. Also British Columbia and Alberta., south to Idaho and California.
  • Europe


  • Clear waters of lakes and ponds with low to medium concentrations of plant nutrients, often rich in lime.


  • Birds: The minute seeds are eaten by waterfowl.




  • Reproduces by seed or by fragmentation
  • Flowers July-September


  • By sprigs


  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Useful as oxygenator in garden ponds, and as shelter for small fishes and aquatic invertebrates.



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Last updated on 26 February, 2004