Photo credit: © Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Brittle Naiad

(Najas minor)

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If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

Brittle naiad, also called brittle waternymph, is a submerged aquatic herb native to Europe and Asia. It gets its name from its fragile stems that can easily break into small pieces and cling to boats, equipment, and waterfowl and be moved to new locations.

Identification

Leaves: Dark green leaves are pointed, oppositely-paired, and become stiff and recurved as they age. Growth appears compact and bushy. The leaves measures about 1 mm (0.04 in) wide and 0.5-3.5 cm (0.2-1.25 in) long. The leaf margins are serrated with 7-15 small but conspicuous teeth along each side. The base is truncate or lobed with fine teeth on the upper margin.

 

Flowers: Small, inconspicuous flowers grow in the leaf axils in late spring and early summer.

 

Fruits/Seeds: Single-seeded fruits mature throughout summer and late fall. They are 1.5-3.0 mm (0.06-0.1 in) long and are slightly curved with rectangular-shaped areolae arranged in longitudinal rows.

 

Stems/Roots: Slender stems may reach up to 2.5 m (8 ft) long and are profusely branched near the apex.

Similar Species

Brittle naiad may be confused with coontail (Ceratophyllum spp) and muskgrass (Chara sp.) It can be distinguished from coontail by its oppositely-paired, unbranched, strap-like leaves. Coontail occurs in whorls of 4-5 which are forked at the tips. It can be distinguished from muskgrass by breaking the stems; brittle naiad stems will remain swollen.

Habitat

This species prefers calm waters such as ponds, lakes, and reservoirs, but may also be found in streams and rivers. It can occur at depths of up to 5 m (16 ft) and tolerate water temperatures over 8°C (46°F). Because it is tolerant of degraded habitats, brittle naiad may have a competitive advantage over many native species.

Spread

Brittle naiad spreads both by seeds and fragmentation. Fragments can cling to boats, trailers, fishing gear, other recreational equipment, and waterfowl and can be spread to new locations. It is also a preferred food source for waterfowl, which consume the seeds and excrete them unharmed in new locations.

Distribution

Brittle naiad is native to North Africa, Japan, Turkey, India and central and eastern Europe. It was first reported in the United States in the Hudson River in 1934, and it may have been intentionally introduced into Cayuga Lake, New York in 1935; although, the reason for introduction is unknown. This plant has spread rapidly in the southeast and Mid-Atlantic regions, and can be found in all Mid-Atlantic states except for Maryland.

 

Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

Brittle naiad forms thick monotypic mats that can shade out other native plant species and reduce the recreational and aesthetic value of lakes, ponds, and rivers. It has even been known to outcompete other harmful invasive plants like Hydrilla.

Video
Note

Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

The Pennsylvania iMapInvasives Program is a partnership of the Western Pennsylvania Conservancy, the Pennsylvania Natural Heritage Program, and NatureServe.

Funding for Pennsylvania iMapInvasives is provided by the Great Lakes Restoration Initiative.

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Pennsylvania Natural Heritage Program, iMapInvasives partner
Great Lakes Restoration Initiative logo, iMapInvasives funding source