Phalaris aquatica L.

Strong perennial clumps, 60–200 cm, from short, knotted rhizome, shoots slightly swollen and ± tuberous at base. Leaf-sheath firm, glabrous, striate, light brown or brownish green. Ligule 4–9 mm, rounded. Leaf-blade 15–60 cm × 5–11 mm, very minutely scabrid, adaxially becoming smooth; margins slightly thickened, minutely scabrid, tapered to long, fine, acuminate tip. Culm 55–180 cm. Panicle (2.5)–3.5–12–(20) × 0.8–2.5–(3) cm, cylindric, oblong or slightly tapered at upper or both ends, occasionally lobed; rachis smooth, branches very sparsely scabrid, hidden. Spikelets 4.5–6.5 mm, light green. Glumes ± equal, 3-nerved, elliptic-lanceolate with deeper green ciliolate wing in upper ½, glabrous, evenly curved towards subacute tip. Ø florets: lemmas unequal, lower 0.5–1 mm, upper 1.2–1.7 mm, lanceolate, acute, sparsely hairy. ☿ floret: lemma 3–3.7 mm, ovate, subacute, with ± sparse, short, fine, silky hairs; palea narrower than lemma; anthers (2.2)–3–4 mm; caryopsis 2.2–2.6 × 1–1.3 mm.

[From: Edgar and Connor (2000) Flora of New Zealand. Volume 5 (second printing).]