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Brittle Naiad

Najas minor

Summary 7

Najas minor, known as Brittle Naiad or Brittle Waternymph, is an annual aquatic plant, a submersed herb, native to Europe, but known to be an invasive species in North America. This plant prefers calm waters, such as ponds, reservoirs, and lakes, and is capable of growing in depths up to 4 meters.

Description 8

This submerged aquatic plant is a summer annual about 2-18" long, although on rare occasions it may become up to 36" long. Individual plants become more branched as they age. The glabrous stems are medium green while young, becoming dark green, more stout, and more brittle with age. Pairs and pseudo-whorls of glabrous leaves about 0.5-3.5 cm. in length occur along these stems, particularly toward their tips. Young leaves are 0.2-0.5 mm. across, medium green, and flexible, while older leaves are 0.5-1.2 mm. across, dark green, stiff, and brittle. The older leaves are usually recurved, creating the appearance of leafy rosettes at the tips of stems. Along each side of the leaf margins are 7-15 teeth that are small in size, but conspicuous. At the leaf bases, there are membranous sheaths about 1.0-2.0 mm. long; each sheath is truncate-fringed along its apex. Mature plants are usually monoecious, rather than dioecious, producing sessile unisexual flowers in the axils of their leaves. These flowers are about 2 mm. long. Individual male (staminate) flowers consist of a single stamen, while individual female (pistillate) flowers consist of a single pistil. Both types of flowers are surrounded by a membranous spathe. The blooming period occurs from mid-summer into the fall. The female flowers are replaced by beaked fruits that are ellipsoid-oblongoid in shape, slightly curved, and about 1.5-3.0 mm. long. Each fruit contains a single seed that is a little shorter than the fruit. Individual seeds are longitudinally ribbed and faintly reticulate. The root system is shallow and fibrous. The fragile stems of older plants are easily broken, creating plant fragments that drift with their seeds in water currents to new locations.

Invasive Spread And Control 9

Brittle naiad was introduced to the United States, where it is considered an invasive species or noxious weed, in the 1900s. Brittle naiad in the United States is established in the Mid-Atlantic States. Established populations are found as far west as Oklahoma and Ontario, Canada in the north. The presence of this plant is a problem because its dense growth covers wide areas, inhibiting the growth of native species of aquatic macrophytes. The thick, clustering growths of brittle naiad can make fishing access or the operation of a boat difficult in a pond or lake. Brittle naiad may spread to new areas by stem fragments carried on a boat's hull, deck, propeller, or trailer. Control measures for brittle naiad include the use of aquatic herbicides, but application of chemicals may not destroy the seeds. Grass carp are another widely used control measure and have been known to readily consume brittle naiad plants. Mechanical harvesting of brittle naiad is difficult, as the brittle stems readily break and are easily disbursed throughout the system. As with most invasive species, prevention of an infestation is easier than eradication.

Identification 9

Najas minor grows in dense clusters and has highly branched stems. These stems fragment easily and this plant is capable of propagation from stem fragments or from small seeds which grow along its stem. The small flowers are located in clusters along the leaf axils. The leaves of the plant are opposite, unbranched, strap-shaped, and are around 4.5 centimeters in length. The leaves have serrations which are visible to the naked eye. This plant is similar in morphology to coontail or slender naiad.

Sources and Credits

  1. (c) John Hilty, some rights reserved (CC BY-NC), http://www.illinoiswildflowers.info/wetland/photos/br_naiad2.jpg
  2. <a href="http://www.pwrc.usgs.gov/WLI/">USDA NRCS Wetland Science Institute</a>., no known copyright restrictions (public domain), https://plants.usda.gov/gallery/large/nami_001_lhp.jpg
  3. (c) John Hilty, some rights reserved (CC BY-NC), http://www.illinoiswildflowers.info/wetland/photos/br_naiad1.jpg
  4. (c) Smithsonian Institution, National Museum of Natural History, Department of Botany, some rights reserved (CC BY-NC-SA), https://collections.nmnh.si.edu/services/media.php?env=botany&irn=10356897
  5. (c) Smithsonian Institution, National Museum of Natural History, Department of Botany, some rights reserved (CC BY-NC-SA), https://collections.nmnh.si.edu/services/media.php?env=botany&irn=10356898
  6. Robert H. Molenbrock, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/c/cb/Brittle_naiad.jpg
  7. Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Najas_minor
  8. (c) John Hilty, some rights reserved (CC BY-NC), http://eol.org/data_objects/29444419
  9. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Najas_minor

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