Showy fleabane is large perennial daisy with erect, simple and clustered stems arising 15-100 cm high. The herbage is nearly glabrous except for ciliate hairs on the midveins and margins of the leaves. The basal and lower stem leaves are thin, oblanceolate or even spatulate, with entire margins. They measure from 8-15 cm long. The lower leaves are broadly petiolate and often deciduous by flowering time. The numerous upper leaves are sessile, almost clasping and narrower (See photos.) The blades are frequently 3-nerved.
The inflorescence is a leafy corymb (or occasionally a large, single and showy head) of 1-13 daisy-like flower heads. The involucre is 6-9 mm high with numerous bracts which are mintuely glandular and sparsely spreading hairy. The tips of the bracts are often loosely spreading. The 65-150 rays are blue, lavendar, violet or occasionally white in color. Individual rays measure 7-18 mm long and are at most 1 mm wide.
Erigeron peregrinus may at first appear similar, but this species has more numerous basal leaves which are present during the period of bloom and it is about half as high. The rays are 2-4 mm wide and the involucral bracts are more densely covered with white, appressed hairs or more glandular.
Showy fleabane is found in open woods, moist meadows and on rocky mountainsides in the foothills to moderate elevations in the mountains.
Showy fleabane may be found from southern British Columbia south through western Washington to northwestern Oregon, then east through eastern Oregon and Washington to Montana and south through Wyoming, Colorado, Utah, eastern Nevada and to northern Arizona and New Mexico. It is also found in the Black Hills of South Dakota and in the Sierra An Pedro Martir of Baja California.
The variety speciosus is found at the western end of the range, from western Montana and northern Idaho west to the Pacific. The variety macranthus is found at the eastern end of the range.