Ranunculus papulentus, commonly known as the large river buttercup, is a buttercup that is endemic to south-eastern Australia.
The large river buttercup is an upright perennial herb 10âÂÂ25 cm in height with underground stolons. The flowering stems are slender and erect, 3âÂÂ30 cm in height. It has 2-4 flowers with spreading, glossy yellow petals.
It has leaves with lamina 2âÂÂ4 cm long. The three primary segments each have 3âÂÂ5 lobes or teeth, or are rarely entire. The petiole is usually 4âÂÂ25 cm long. The petals are 7âÂÂ12 mm long and 2âÂÂ4 mm wide. The nectary lobes are elliptical or semicircular. It usually has 12âÂÂ36 achenes, 1.7âÂÂ3.6 mm long, with the lateral faces irregularly wrinkled or pitted, or rarely smooth, and when mature often pale and thickened along the dorsal ridge.
It has been recorded from New South Wales, Victoria, South Australia and the Australian Capital Territory. It occurs in freshwater wetland environments, on mud or in pools.
Flowering may occur from spring to autumn. The plant has a rhizomatous habit which aids its spread.