Western swamp buttercup is an attractive perennial wildflower of wet places with several spreading to erect stems from 20-60 cm high. The stems are hollow and are usually branched. The herbage is highly variable, ranging from sparsely to heavily haired. The leaves are mostly basal with a few reduce leaves on the stems. The basal leaves have long petioles to 25 cm long and blades from 3-8 cm long. The blades are pinnately compound with 3-7 leaflets. Individual leaflets are irregularly toothed and lobed into linear, ovate, acute or obtuse segments.
The 5 petals are yellow (occasionally reddish or purplish as noted below) and obovate or oblong in shape, measuring 9-18 mm long. The 5 sepals measure from 6-9 mm and are greenish or often tinged with purple. They are usually reflexed, covered with long straight hairs, and soon deciduous. The stamens number from 50-70.
Variety orthorhynchus: The yellow petals are tinged with red or purple and over twice as long as wide.
Variety platyphyllus: The petals are entirely yellow and are rarely as much as twice as long as wide.
Western swamp buttercup is found in wet meadows, ditches, and slow streams on both sides of the Cascade Mt range.
Western swamp buttercup may be found from Alaska south to California and east to Montana, Wyoming and Utah.In the Columbia River Gorge it may be found between the elevations of 500'-2300' from the Wind River east to the Klickitat River.