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Montana Field Guide

Montana Field Guides

Brittleleaf Naiad - Najas minor
Other Names:  Brittle Waternymph, Brittle Water Nymph

Aquatic Invasive Species
Non-native Species
Not Documented

Global Rank: GNR
State Rank: SNA
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
Najas minor is not known to occur in Montana. A conservation status rank is not applicable (SNA) because the plant is not a suitable target for conservation activities. The purpose of this profile is to provide awareness and education to prevent its introduction into Montana. Preventing deliberate plantings and spread from plant fragments are the best means to keep this plant out of Montana’s waters.
General Description
PLANTS: Perennial, aquatic plant with submersed vegetation that grows in fresh or brackish waters. Source: Flora of North America (FNA) 2000.

LEAVES: Stems are highly branched in their upper portions. Leaves submerged, 0.5-3.5 cm, and become recurved and stiff with age. Space between leaves ranges from 0.5 to 5.8 cm. Sheath is 1-3 mm wide, truncate to auriculate, with multi-cellular teeth. Prickles lacking. Source: FNA 2000.

INFLORESCENCE: Male and female flowers are separate on the same plant. 1-2 flowers occur in the leaf axils. Male flowers tend to occur on upper portions and female flowers tend to occur on lower portions of stems. Source: FNA 2000.

Flowering summer to fall (FNA 2000).

Diagnostic Characteristics
Brittleleaf Naiad is not documented in Montana, but is considered a more distinctive species of Najas (FNA 2002). In Montana our two native species are Guadalupe Water-nymph [Montana Species of Concern] and Slender Naiad. Users of the Montana Field Guide should consult eFlora (the on-line version of the Flora of North America) and/or Flora of the Pacific Northwest-2nd Edition (Giblin et al. [eds.] 2018).

Young, sterile specimens cannot be accurately identified (FNA 2000).

Brittleleaf Naiad - Najas minor, NOT DOCUMENTED IN MONTANA
*Leaves: At maturity, blades recurve and become stiff with age. Prickles lacking.
*Seeds: Broader than long and with areoles arranged in longitudinal rows – like the rungs of a ladder.

Guadalupe Water-nymph - Najas guadalupensis, SOC
*Leaves: 5-15 mm long with minutely toothed margins. Ribbon-like with short tapering tips and expanded bases. Additional leaves are often found in the axils. Prickles lacking.
*Seeds: Dull and coarsely pitted, with a honeycomb surface.

Slender Naiad - Najas flexilis, Native
*Leaves: 10–35 mm long with a dilated base that is 2–3 mm wide. From about their mid-section, leaves have a long taper that terminates in a long slender point. Prickles lacking.
*Seeds: Smooth, shiny, and sometimes minutely spotted.

Spiny NaiadNajas marina, Exotic
*Leaves: Coarsely serrated margins with 8 to 13 teeth on each side of the blade. Prickles can be found on the abaxial (lower) surface of the blade.
*Seeds: Ovoid, reddish brown, and pitted with areoles (outer two coatings of the testa) irregularly arranged, not in distinctive rows or not ladder-like. Seeds are longer than broad with the end walls slightly raised.

The Najas genus is sometimes placed in the Family Hydrocharitaceae, also known as the Waterweed or Frog’s-bit Family.

Range Comments
Plants are introduced into North America: Alabama, Delaware, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Massachusetts, Mississippi, Missouri, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Vermont, Virginia, and West Virginia (FNA 2000). The Natural Resources Conservation Service PLANTS website reports it has been found in California, Michigan, Texas, Wisconsin in the U.S. and Ontario, Canada ( as of June 27, 2019).

It has not been documented in Montana, the Pacific Northwest, or upper Great Plains.

For maps and other distributional information on non-native species see:
Nonindigenous Aquatic Species Database from the U.S. Geological Survey
Invasive Species Habitat Tool (INHABIT) from the U.S. Geological Survey
Invasive Species Compendium from the Centre for Agriculture and Bioscience International (CABI)
EDDMapS Species Information EDDMapS Species Information

Ponds, lakes, and slow moving streams (FNA 2002).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Reproductive Characteristics
FLOWERS and FRUITS [Adapted from FNA 2000]
Male flowers are 1.9-2.2 mm long. Their involucral bracts are 2-lobed, beaked (0.4-2.1 mm long). Female flowers are about 2.2 mm long. Pistils have 1 style (1-1.2 mm) and 2-lobed stigmas.

Fruits dehisce by decay of the ovary wall. Ovary wall is delicate and encloses the seeds. Seeds are slightly recurved, purplish, fusiform, 1.5-3.0 mm by 0.5-0.7 mm. Style is centered on the seed’s apex. Testa is dull, 3-cells thick, and pitted. Areoles form from the outer two layers of the test. Areoles are regularly arranged in about 15 longitudinal rows (like the rungs of a ladder) and that are wider than long, with end walls that are not raised.


  • Literature Cited AboveLegend:   View Online Publication
    • eFloras. No Date. Published on the Internet Missouri Botanical Garden Herbarium, St. Louis, Missouri and Harvard University Herbarium, Cambridge, Massachusetts
    • Flora of North America Editorial Committee (FNA). 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.
    • Hitchcock, C.L. and A. Cronquist. 2018. Flora of the Pacific Northwest: An Illustrated Manual. Second Edition. Giblin, D.E., B.S. Legler, P.F. Zika, and R.G. Olmstead (eds). Seattle, WA: University of Washington Press in Association with Burke Museum of Natural History and Culture. 882 p.
    • U.S. Department of Natural Resources and Conservation (NRCS) - PLANTS database. 2006-2019. The Plants Database. USDA Natural Resources Conservation Service (USDA, NRCS). National Plant Data Center, Baton Rouge, Louisiana 70874-4490 USA.
  • Web Search Engines for Articles on "Brittleleaf Naiad"
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Citation for data on this website:
Brittleleaf Naiad — Najas minor.  Montana Field Guide.  .  Retrieved on , from