Stems floating or prostrate, glabrous, rooting at proximal nodes. Leaves: basal leaves seldom present, cauline leaf blades semicircular to reniform, 1-6×-lobed, parted, or dissected 1.2-7.3 × 1.9-10.8 cm, base truncate or cordate, segment margins entire or crenate, apex rounded to filiform. Flowers: receptacle sparsely hispid; sepals 5, spreading or weakly reflexed, 5-7 × 3-6 mm, glabrous; petals 5-6(-14), 7-12 × 5-9 mm; nectary scale variable, crescent-shaped, funnel-shaped, or flaplike; style 0.8-1.2 mm. Heads of achenes ovoid, 8-10 × 7-8 mm; achenes 1.8-2.2 × 1.6-2.2 mm, glabrous; beak lanceolate, straight, 1-1.8 mm. 2 n = 32. Flowering late spring-summer (May-Aug). Shallow water or drying mud; 0-1500 m; Alta., B.C., Man., N.B., Ont., Que.; Ala., Ark., Calif., Conn., Del., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., Nev., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., Wis., Wyo. The Fox tribes used Ranunculus flabellaris as a cold remedy and a respiratory aid (D. E. Moerman 1986).