Conium maculatum L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stem freely branched, to 3 m, purple-spotted; lvs 2–4 dm, broadly triangular-ovate, 3–4 times pinnately compound, the ultimate segments ovate-oblong, 4–10 mm, toothed or incised; umbels 4–6 cm wide, the terminal one blooming first but soon overtopped by others; fr broadly ovoid, 3 mm, the pale brown ribs very prominent when dry; 2n=22. Native of Eurasia, now widely intr. as a weed in waste places from Que. to Fla., w. to the Pacific. This is the hemlock of classical antiquity. All parts of the plant are very poisonous.