Cyperaceae: Eleocharis compressa
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Family Name
Cyperaceae
Common Name
Flat-stem spike-rush
Description
Eleocharis compressa is an annual to perennial herbaceous sedge from a fibrous root system. Stems (culms) are erect, slender, and usually laterally compressed (flattened) in cross-section, ranging from 10–50 cm tall. Leaves are reduced to narrow sheaths at the base of the stem, with no true leaf blades. The ligule is typically absent or represented by a small membrane or fringe of hairs at the junction of sheath and stem. Flowering occurs from summer to early fall (July–September). The inflorescence consists of a single terminal spikelet about 5–15 mm long, narrow and cylindrical, containing numerous tiny flowers. Each flower is subtended by a scale (a modified bract) about 2–3 mm long, ovate to lanceolate in shape, greenish to brownish in color. Flowers have no petals or sepals but possess three stamens and a single pistil. The fruit is a small, lens-shaped achene, about 1–2 mm long, brown at maturity, ripening late summer into fall. Flat-stem spike-rush is native to South Dakota, commonly occupying wetlands, shallow ponds, marshes, and wet meadows statewide, especially in the eastern and central regions.
Horticulture Notes
Seed Collection: Seeds mature when spikelets dry and become brown; collect late summer to early fall.
Germination: Seeds germinate readily without dormancy; best sown in moist soils in spring or early summer.
Vegetative Propagation: Not commonly propagated vegetatively; reproduces primarily by seed.
Soils: Prefers saturated to wet soils in marshes, ponds, and shallow waters.
Light: Thrives in full sun to partial shade.
Water: Requires saturated to standing water conditions for optimal growth.
Additional Notes
Flat-stem spike-rush plays an important ecological role in wetland habitats, contributing to soil stabilization and providing habitat for aquatic invertebrates and waterfowl.