Stems arising 0.7-1.5 m above the water (this sometimes over 1 m deep); lvs seldom over 1 cm wide; ligule 3-5(-10) mm; panicle narrow, the lower branches with usually 5-15 staminate spikelets; awns of the pistillate lemmas 1.5-4 cm. Que. and N.B. to Pa., w. to Io. and Minn. (Z. aquatica var. angustifolia)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.