Cow parsnip is one of the largest forbs in Denali's flora, with wide flat-topped umbels of white flowers and massive palmately-divided leaves. The plant grows to 1.5 m high from thick taproot, found in meadows and forest openings, primarily in the subalpine zone, and much more commonly in the maritime-influenced areas south of the Alaska Range. Like many members of the Apiaceae family, the petioles form an inflated sheath around the stalk. Leaves are palmately divided into 3 leaflets, these segments further lobed and with serrate margins. The whole leaf is 20-50 cm across. The stout stems are ridged and dense with short white hairs. Umbels grow from leaf axils, and the buds look like massive swellings. Small bracts with extremely long, narrow tips subtend the umbel, dehiscing after the flowers open. Umbels are 10-20 cm across, arising terminally from the central stalk as well as from axillary buds. Plants either produce all male (staminate) or bisexual flowers. In either case, flowers have five white petals. Flowers produce an ovate to heart-shaped fruit, flattened, 7-12 mm long, with a strong center vein and raised margins, papery and transparent otherwise. The whole plant has a strong, skunky smell. While other members of the Apiaceae can look similar, none are as large as cow parsnip.
Cow parsnip is biennial. Flowers are protandrous, meaning pollen is released before the carpels are fertile, preventing self-fertilization (Konuma and Yahara 1997). Timing of pollen release and stigma receptivity varies by habitat. Flowers usually appear in mid-summer.
Cow parsnip is andromonoecious, the flowers of one plant either staminate or bisexual (Cruden 1976). This species is insect-pollinated, elsewhere in its range by bees and flies (Cruden 1976). The flattened fruit is dispersed by wind and gravity.
Cow parsnip is a large parsley relative common in moist sunny woodland clearings and margins where it may present a trail hazard from a potentially photo-toxic oil produced on its leaves and stem surface. The Dena'ina used boiled roots as a poultice or to make a tea for drinking or as a wash, apparently with antibiotic and numbing effects (Kari 1995). Ailments addressed include internal pain, skin abrasions, inflammation, and infections including blood poisoning. The root could be chewed as a preventative medicine and toothaches were dealt with by placing a raw root on the offending tooth until it disintegrated. The Yup'ik eat the peeled stem raw (Jernigan et al. 2015).
Cow parsnip is an amphi-Beringian species that occurs throughout most of North America, except it does not reach the Gulf Coast states such as Texas and Florida. In Alaska, the species is especially common in maritime-influenced areas of Southcentral, Kodiak Island and Southeast regions, its range extending to Attu Island and the Kuskokwim Mountains. There are also isolated localities on the Seward Peninsula and in the Brooks Range, and the Ogilvie Mountains. Cow parsnip is common and abundant on the south side of the Alaska Range in Denali, with occasional localities on the northern slopes and northeastern foothills of the park.
In Denali, this species is found from elevations of 83 to 1310 m, frequency peaking dramatically at 700-900 m. Found on moderate slopes, uncommon in flat areas and inclines above 28 degrees. Predominantly on south-facing slopes. Plants on northern aspects have a lower range of elevations (this may be due to sampling, i.e. less north-facing specimens).