The Louisiana quillwort (Isoetes louisianensis) is a small, grass-like aquatic plant of the family Isoetaceae. It is "one of the rarest quillworts in North America." It occurs in only five locations in St. Tammany and Washington Parishes of Louisiana and some spots in southern Mississippi (United States). It is federally listed as an endangered species, partly due to its highly restricted range.
The Louisiana quillwort occurs predominantly on sand and gravel bars on small to medium-sized streams. These plants live for periods underwater. They are regularly inundated as much as 50 centimeters (20 inches) following rains, and may be inundated for long periods in wet seasons. Its habitat follows roughly along the Bogue Chitto River. Associated plants include primrose-leafed violet (Viola primulifolia), bulrush (Scirpus divaricatus), water-willow (Justicia lanceolata), yellow-star grass (Hypoxis leptocarpa), yellow-eyed grass Xyris sp. and sedge (Carex sp.), swamp tupelo (Nyssa sylvatica var. biflora), water tupelo (Nyssa aquatica), sweetbay (Magnolia virginiana), bald cypress (Taxodium distichum), swamp laurel oak (Quercus obtusa), red maple (Acer rubrum), loblolly (Pinus taeda), ti ti (Cyrilla racemiflora), fetterbush (Lyonia lucida), and winterberry (Ilex verticillata).
The Louisiana quillwort was described recently, in 1973, and was listed as an endangered species in 1992.
- "Isoetes louisianensis". NatureServe Explorer. NatureServe. Retrieved 2007-12-19.
- I. louisianensis. Center for Plant Conservation.
- USFWS. Determination of Endangered Status for the Plant Isoetes louisianensis (Louisiana Quillwort). Federal Register October 28, 1992.