A perennial, smooth marsh herb with stout, erect, branching hollow stem, 2 to 6 feet high. Lower and basal leaves long petioled, finely divided; petioles sheathing the stem at their bases; segments of the leaves seven to seventeen in number, linear or lanceolate, 1 1/2 to 5 inches long, one-eighth to 1 inch wide, long pointed at the apex, margins sharply toothed. Flowers white in large compound umbels, 2 to 3 inches broad; primary rays of the umbel eight to twenty in number, one-half to 11/2 inches long; involucral bracts small and narrow; calyx teeth minute, petals inflexed at the apex. Fruit ovate, compressed, about one-eighth of an inch long, the ribs prominent.
In marshy places, Nova Scotia to British Columbia, south to Florida, Louisiana and California. Flowering from July to October.
Memoir 15 N. Y. State Museum
Hemlock Water Parsnip - Slum cicutaefolium