Cow parsnip is a biennial that spreads by seed. Its habit is tall and spreading, growing up to 5 feet tall and wide. Leaves are enormous, up to 16 inches long and 12 inches wide. Each leaf is made up of 3 leaflets, with the terminal leaflet generally larger than the basal 2. Leaf margins are serrated and lobed. Stems are slightly ridged and hirsute (very hairy). This is in stark contrast to the smooth and glaucous stems of poison hemlock. Large swollen regions of the stem are conspicuous, and are really just flower buds waiting to emerge. These swellings can be as large as an orange. Flowers occur in a flattened compound umbel, typical of plants in the carrot family.
Part of the Butterfly Bed & Breakfast Project.