Sweet marsh groundsel is an erect stemmed wildflower, with one to several stems arising from 30-100 cm in height. Its herbage is smooth, with thick succulent leaves that are elliptic or widely oblanceolate in outline. The lower leaves range from 6-25 cm long and 2-7 cm wide. The upper leaves become sessile and reduced in size.
The numerous flower heads are found in a tight inflorescence. The involucre of each head is 6-9 mm high with black-tipped bracts. The heads typically lack ray flowers, although it is possible the head may have as many as 5 yellowish rays. If the rays are present, they are about 8 mm long.
Sweet marsh groundsel is found in wet meadows from the foothills into the mountains. .
Sweet marsh groundsel is found from southern British Columbia southeast of the Cascade Mts to central and northeastern Oregon, and then east across central Idaho to Fremont County, Idaho.
In the Columbia River Gorge, it is found between the elevations of 1600'-2300' in the Major Creek Plateau east of White Salmon, WA.
