American thorow-wax is a slender herb with narrow leaves and small umbels of yellow flowers that grows in warm, dry sites in the hills and mountains north of the Alaska Range crest in Denali. Plants grow 10-30 cm tall, from a branching caudex. The parallel veined leaves are alternate, simple, and oblong-narrowly lanceolate in shape, 2-25 cm long with whitish blush. The inflorescences are compound umbels, each head with 1-8 rays, the terminal umbels compact and rounded. There are one or several leafy bracts below the umbel, and smaller bracts beneath each secondary umbel. The flowers have yellow petals with the margin inrolled. Flowers produce two dry fruits, 5 mm, with short ribs. Bupleurum americanum is the only species of plant in Denali with umbels of yellow flowers and linear leaves. The leaves can look similar to those of Zigadenus elegans, which occurs in very similar habitats to Bupleurum americanum, but the flowers are very different.
Bupleurum americanum is perennial and typically flowers in mid-summer.
This species is monoecious with bisexual flowers. The flowers are insect pollinated and the fruits are winged, letting them be wind-dispersed.
American thorow-wax is an amphi-Beringian species. In North America, the species ranges southward from Alaska through the Rockies, including Yukon and Northwest territories, B.C. and Alberta, reaching Arizona in the south. In Alaska, this species grows in the interior and arctic regions, including some inland localities on pingos on the Arctic coastal plain. Bupleurm americanum is a common member of steppe communities on south-facing river bluffs and in dry, grassy subalpine meadows of interior mountain ranges, it is absent in the Aleutians and south of the Alaska Range. In Denali, this species occurs sporadically on the north side of Alaska Range, and most frequently in mountains in northeastern corner of the Park.