Phalaris aquatica

Shortly rhizomatous perennial, lower internodes often swollen, culms erect, to 160 cm high. Leaves smooth and glabrous; blade to 30 cm long and 20 mm wide; ligule obtuse, membranous, to 10 mm long. Panicle dense, cylindric, (2–)5–15 cm long. Spikelets 5.5–7 mm long; glumes 3-nerved, subequal, dorsally winged; sterile lemmas linear, the lower up to one-quarter (sometimes lacking), the upper to one-third (but often less) as long as fertile lemma; fertile lemma lanceolate, 3–4 mm long, with appressed hairs. Flowers Nov.–Jan.