Lepidosperma longitudinale is commonly known as the pithy sword-sedge or pith saw sedge. It is an evergreen species of sedge that is native to swampy areas of most Australian states. It was described by French botanist Jacques Labillardière in 1805. The preferred habitat of L longitudinale is freshwater areas such as swamps, lake edges, floodways, creekbanks and seeps. The plant tends to spread with its creeping rhizomes to form new stems to form dense monoculture colonies.