Tidal Marsh Flat Sedge

Kükenthal (1936) assigns Cyperus serotinus and his sect. Serotini to subg. Juncellus almost solely because of the distigmatic flowers. Typically, species of subg. Juncellus have pseudolateral, capitate inflorescences and thus C. serotinus with its compound inflorescence fits poorly into this group. It is therefore included here in subg. Cyperus (cf. Kükenthal l.c.: 40, 1935). Immature specimen from Peshawar (Masih 30) is exceptional having very narrow, many-spiked distal cluster of spikes; variation of C. serotinus requires further study.

Herbs, perennial, stoloniferous; stolons terminated by tubers. Culms trigonous, 50–100 cm × 5–8 mm, glabrous. Leaves 3–6, V-shaped, 20–50 cm × 5–8(–10) mm. Inflorescences: spikes not appearing lateral, rays 5–8, 2–7(–12) cm; bracts 3–4, ± horizontal to ascending at 45°, V-shaped, 5–25 cm × 1.5–8 mm; spikes 1–4, ovoid, 2–4 × 2–3 cm; rachis 1–2.7 cm, smooth or hispidulous; rachilla persistent, wingless or with hyaline wings scarcely 0.1 mm wide. Spikelets 7–14, flattened, lanceoloid, 10–20 × 2–2.5 mm; floral scales 10–30, laterally dark brown to reddish brown, medially greenish, laterally 5–9-ribbed, ovate-deltate; anthers 3, 0.5 mm; styles 0.5 mm; stigmas 1.2–1.6 mm. Achenes brown, sessile, ellipsoid, 1.4–1.6 × 1.4–1.5 mm, apex obtuse, apiculate.

Perennial, 40-60 cm. Rhizome short, emitting creeping stolons, 2-3 mm diam., covered by brown scales, shorter than internodes. Stem 3.5-5 mm diam., sharply trigonous, grey green, smooth. Leaves equalling stem; sheaths up to 15 cm, all with blades, green or grey green, often with some reddish tint, mouth margin almost straight; blades up to 60 cm, 4-8 mm wide, flat or folded, keeled, margins and keel smooth, apex long-attenuate, scabrous. Inflorescence a compound anthelodium, 6-20 cm; bracts 2-4 foliose, up to 50 cm; primary branches 4-7, up to 16 cm; secondary anthelodia 25-50 mm, conical; secondary branches to 10 mm; cluster of spikes rounded or cylindrical, 10-40 mm, with 7-21 spirally aranged spikes; spikes 5-15 x 2.5-4 mm, turgid, obovoid to almost parallel-sided, with 10-25 glumes, glume-like bract c. 1 mm, acute, glume-like prophyll obtuse, bi-nerved, base corky, swollen; rachis 4-angled, c. 1 mm wide, c. 0.7 mm thick, compressed, internodes 1.2 mm, narrowly winged; glumes 2.2-2.8 mm, widely cymbiform, obtuse, sides dark reddish brown, sometimes greenish brown, margins scarious. Stamens 3; stigmas 2. Nut 1.4-1.6 x 1.2-1.3 mm, lenticular, widely obovoid or ellipsoid, brown, glossy, finely reticulate.

introduced; Del., N.J., Pa.; Eurasia.

Distribution: From S France and east C Europe to Vietnam, Taiwan and Japan; Turkey, Caucasus, Uzbekistan, Tadjikistan, Pakistan and NW India.

Fl. Per.: (April-) July - September.

Fruiting summer.

Tidal marshes; 0m.

In streams, irrigation channels, ditches, rice fields.

Chlorocyperus serotinus (Rottbøll) Palla; Juncellus serotinus (Rottbøll) C. B. Clarke

Juncellus serotinus (Rottb.) C. B. Clarke, in Hook. f., Fl. Brit. Ind., 6: 594. 1893. Chlorocyperus serotinus (Rottb.) Palla, Allg. Bot. Zeitschr. 6: 201. 1900. Duval-Jouvea serotina (Rottb.) Palla in W.D.J. Koch, Syn. deutsch. schweiz. Fl., ed. 3, 3: 2556. 1903; C. monti L. fil., Suppl. Pl.: 102. 1781. Pycreus monti (L. f.) Reichenb. in Mössler, Handb. Gewächskunde, Ed. 2, p. 1802. 1829; Kükenthal, in Engler, Pflanzenr., IV.20, 101: fig. 36. 1936. Ovczinnikov, Fl. Tadjik. SSR, 2: tab. 1, figs. 5-7. 1963.

Cyperus serotinus occurs naturally in Eurasia, but has been introduced as an alien species in parts of the eastern USA. This plant is typically found in marshes, irrigation ditches and rice fields. The species is often controlled in its alien range with herbicides such as Tetrahydropyrimidinones.

This perennial herb is stoloniferous, with the stolons terminated by tubers. Culms trigonous, 50 to 100 centimetres in height.

Cyperus serotinus is a species of sedge that is native to parts of Europe and Asia.

The species was first formally described by the botanist Christen Friis Rottbøll in 1773.