Glyceria maxima

Vigorous, long-rhizomatous perennial, culms stout, ascending to erect, to 2.5 m high. Leaf-blades to 60 cm long and 18 mm wide; sheaths closed toward base, transverse veins indistinct or lacking; ligules 3–6 mm long, obtuse, but often with a short central point. Inflorescence a loose contracted or open panicle, 12–45 cm long. Spikelets 4–10-flowered, 5–12 mm long; lower glume 2–3 mm long, upper glume 0.5–2 mm longer than lower; lemma 7-nerved, ovate, 2.5–4 mm long, firm, rounded at apex, scabrous; palea shorter than or equal to lemma. Flowers Nov.–Feb.