Eleocharis quadrangulata, commonly known as Squarestem Spikerush, is a deciduous perennial grass native to wetlands such as marshes, fens, wet meadows, and along the edges of ponds and streams in the Eastern and Central United States, Ontario, and parts of Mexico. It typically grows to a height of 0.5 to 1 meter. The plant is characterized by its spongy, compressible stem that is a few millimeters wide and sharply four-angled, giving the plant its common name. The inflorescence consists of a single spikelet, 1.5 to 7.5 centimeters long, composed of several flowers enveloped in light brown bracts. The flowers are not particularly showy but are interesting upon close inspection.

Squarestem Spikerush is valued for its ability to stabilize soil and filter water in wetland restoration projects. It is also used in water gardens and naturalized areas where its adaptability to wet conditions is beneficial. This plant thrives in full sun but can tolerate partial shade, requiring high amounts of water and preferring soils with slow or standing drainage. While it is not prone to many diseases, it can become invasive if conditions allow for unchecked growth.CC BY-SA 4.0