Invasive Aquatic Plant Watch: Brittle Naiad

August 4, 2010

Brittle naiad, brittle waternymph, or Minor naiad (Najas minor) is native to Europe and was introduced to North America in the 1930s. It has been recorded in 26 states, mostly east of the Mississippi River, and Ontario, Canada. Though patchily distributed throughout the states where found, it has a rapid growth rate. A Connecticut Agricultural Research Station Invasive Aquatic Plant Program lake survey in 2004 found it in 10 lakes, by 2005 it was in 20, and increased to 23 in 2006. It reproduces by seeds from flowers that develop in late spring to early summer and fragmentation (thus its common name).The tiny seeds are spread readily by waterfowl, boats, and boat trailers.

Brittle naiad grows in water 15 cm to 2 meters in depth. The plant often appears compact and bushy but can reach one meter in length. The leaves are usually stiff, curled, and pointed with spines along the edges. It is sometimes confused with other naiads, but is the only Najas species whose spines on the leaf margins are visible to the naked eye. Another plant, coontail (Ceratophyllum demersum), is sometimes mistaken for the brittle naiad, however coontail’s leaves are arranged in whorls of four or five and the brittle naiad has opposite leaves.

Naiads, or waternymphs, are widespread throughout North America, with five native species and three introduced. They are generally considered to be one of the most important food sources for waterfowl, which eats the entire plant, and offer habitat for aquatic invertebrates and small fish.

Two other introduced naiads are Wright’s waternymph (N. wrightiana), in Florida and the ricefield waternymph (N. graminea), in California. As with all invasive plants, prevention is the best management tool. To avoid unwanted hitchhikers, rinse boats, trailers, tires, and wheel wells with a power hose, or use a dilute bleach solution, when leaving a lake. Any other equipment that was put in the water, such as snorkels, fins, boots, and waders should be also be rinsed.