Cow Parsnip is a large, fairly attractive perennial wildflower with a single, stout and erect stem from one to three meters high. The lower stems may be lightly haired, but the underside of the leaves and upper stems near the inflorescence are thinly tomentose to woolly-villous. The stems are hollow and heavily veined. The large leaves are once-ternate with broad petiolate leaflets which are palmately veined with coarsely toothed margins. The blades of the leaflets are roughly 10-30 cm long and about as wide, with the central leaflet the largest.
The inflorescence is a compound umbel (See photo below.) with 10-30 unequal rays, each from 5-10 cm long. The flowers are white, with the outer flowers of the outer umbellets having large, deeply obcordate petals. The fruit are broadly elliptic to obovate in shape with a notch at the apex, and range from 8-12 mm long and 7-9 mm wide. Cow Parsnip is a prolific self-seeder.
Cow Parsnip is found along streambanks and on moist ground in shady woods.
Cow Parsnip is found from Alaska south to California and Arizona and east to Newfoundland and hence south to Georgia. It is also found in Siberia and the Kurile Islands.
In the Columbia River Gorge, it is found between the elevations of 100'-4200' from the Sandy River in the west to near the Klickitat River in the east.
Compound leaf of the cow parsnip.