Wild parsnip

This herbaceous biennial plant is 2-5' tall, branching occasionally. The stems are glabrous, angular, and furrowed. The alternate leaves are oddly pinnate, consisting of about 9 leaflets that are largely hairless. The lower compound leaves are up to 18" long and 6" across; they have long petioles. The upper compound leaves are substantially smaller; they have short petioles. The individual leaflets are up to 3" long, 2" across, and ovate or elliptic in outline; they often have cleft lobes and coarse teeth along the margins.
The upper stems terminate in compound umbels of tiny yellow flowers. Each compound umbel has a long naked peduncle and spans about 3-8" across when fully mature; it is flat-topped. A compound umbel consists of about 15-25 umbellets, and each umbellet has about 12-35 flowers. Both floral bracts and floral bractlets are absent. Each flower is about 1/8" across, consisting of 5 yellow petals, a greenish yellow nectar pad, and insignificant sepals. The tiny petals are initially folded toward each other, but they eventually curve outward. The blooming period typically occurs from late spring to mid-summer and lasts about 1-2 months; a few plants may bloom later in the year. Each flower is replaced by a schizocarp containing a single seed. The seeds are flattened and winged; they are blown about by the wind. The root system consists of a stout fleshy taproot with a distinctive aroma that is quite similar to cultivated parsnips. This plant spreads by reseeding itself.