Alopecurus geniculatus L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Perennial; culms 2–8 dm, usually decumbent, sometimes rooting at the nodes; infl 3–5 cm × 4–6 mm, often purple-tinged; glumes as in no. 5 [Alopecurus carolinianus Walter]; awn attached halfway between the base and the middle of the lemma, geniculate, exserted 1.5–3.5 mm; anthers 1.3–2 mm; 2n=28. In mud and shallow water; a Eurasian or perhaps circumboreal sp., found throughout most of our range as an apparent introduction.