Wild Parsnip (Pastinaca sativa)
This is actually the same plant as the garden parsnip, though not bred for flavor. It is often found on roadsides and at the edge of the woods, frequently growing almost as tall as a person. These were growing in a clearing in Schenley Park, where they were blooming in early June. The combination of tall, thick stems and broad compound umbels of yellow flowers is distinctive; Golden Alexanders, another member of the same family with yellow flowers, is a much more delicate plant.
Gray describes the genus and the species.
PASTINÀCA L. PARSNIP. Calyx-teeth obsolete. Fruit oval, very much flattened dorsally; dorsal ribs filiform, the lateral extended into broad wings, which are strongly nerved toward the outer margin; oil-tubes small, solitary in the intervals, 2-4 on the commissure; stylopodium depressed. — Tall stout glabrous biennial, with pinnately compound leaves, mostly no involucre or involucels, and yellow flowers. (The Latin name, from pastus. food.)
P. satìva L. Stem grooved; leaflets ovate to oblong, cut-toothed. — Waste places, open rich soil, etc. (Nat. from Eu.)