Scleria lacustris (Wright's nut-rush)
invasive and spreading in seasonal marshes of Florida

Scleria lacustris (Wright's nutrush) is an introduced sedge of increasing ecological concern in Florida. First collected in 1988, its distribution now extends to more than twenty natural areas in four major drainage regions (link to map).

Freshwater marshes and lake shorelines characterized by seasonal water level fluctuations appear most vulnerable to invasion by Scleria lacustris.  Seedlings are believed to emerge and establish during spring when marshes are dry.  Juvenile plants adapt readily to the influx of water during the rainy summer months.  As late summer surface water levels rise, emergent plants flower and grow to heights of 200 cm. In autumn mature plants sprawl across the water as their nutlets ripen and disperse (Fig. 8).

Scleria lacustris is native to scattered regions of Africa and the Neotropics.  Its source of introduction to Florida is unknown.  Birds and airboats are suspected to aid in dispersal of the shiny nutlets, although transport by water through drainage systems could be most important, leaving vast conservation marshes of southern Florida at risk.

Identification Tips for Scleria lacustris
 (Wright's nut-rush)

Nutlets – Oval to elliptic and somewhat triangular in outline. White to mottled gray, hard, and porcelain-like, the nutlets contain only a single seed.  Nutlets mature on heavy branching panicles from August to December (Fig. 5). In late winter nutlets can be found under litter of dry stalks (Fig. 1) or in the surface substrate. Roots, stems and other vegetative portions of plants do not persist over winter; however the nutlets ensure a viable seed bank for reoccurrence in spring.

Seedlings – The three angled stems and 3 ranked leaves are typical for sedges, however, nutlets remaining attached to young seedlings lend positive identification (Fig. 2).

Roots – Dark red, stout and shallowly anchored in the substrate. Also, fibrous floating roots appear at nodes when stems become inundated (Fig. 3).

Stems - As thick as 2.5 cm at the base and three angled throughout.  Developing spongy interiors as plants emerge from water (Fig. 4). Dry land plants are smaller in stature (60 –150 cm), often with thinner, multiple stems. All stems are streaked with red, especially at the base.

Leaves – Pleated, smooth and shiny.  Leaf width to 2.5 cm, length to 60 cm and tapering to a point. Prickles along the leaf and stem margins impart a deep, slicing wound when handled (Fig. 7).

Flowers - Displayed July through September on bisexual spikelets.  Spikelets are spirally to alternately arranged on branching inflorescences (flowers have matured to nutlets in Fig. 6).

Current Distribution Map
Scleria Flyer w/ photo collage - (Acrobat PDF format, 435 kb)

Report Occurrences: Colette Jacono@usgs.gov or phone 352.264.3484.

Further Information:  Jacono, C.C.  2001. Scleria lacustris (Cyperaceae), an aquatic and wetland sedge introduced to Florida. Sida, Contributions to Botany 19(4):1163-1170.

May 2005