General: Aquatic or amphibious, perennial herb, rooting from nodes of lower stems, roots slender, fibrous; stems slender, simple to branched, floating or trailing, to 50 cm long, smooth or hairy, hollow.
Leaves: Basal leaves absent; stem leaves alternate, kidney-shaped to circular, 3-lobed or -parted, 0.6-6.5 cm long, 1-9 cm wide, bases heart-shaped, the segments 1- to 3-times lobed to dissected, entire or round-toothed, tips rounded; submerged leaves sometimes deeply dissected into linear or thread-like segments; stalks to 5 cm long.
Flowers: Inflorescence of solitary flowers from leaf axils, sometimes the terminal one a few-flowered cyme, the stalks 1-5 cm long; receptacle sparsely stiff-hairy; petals 5 or more, distinct, yellow, 3-7 (10) mm long, 2-5 mm wide, egg-shaped, nectary on upper surface, the nectary scale variable; sepals 4 or 5, spreading or bent back from base, early deciduous, 2-5 mm long, 2-4 mm wide, smooth or sparsely long-hairy; stamens 10-45; pistils 20-70.
Fruits: Achenes, numerous in an egg- to globe-shaped head 3-8 mm long, 3-7 mm wide, the achenes egg-shaped, slightly flattened, 1-1.6 mm long, 1-1.2 mm wide, smooth, whitish-puffy over the lower 1/2 to 2/3 of the circumference; beaks persistent, lanceolate to thread-like, flattened, straight, 0.4-0.8 mm long.
Notes: There are no reliable morphological differences for recognition of infraspecific taxa (Scott 1974). This species is closely related to R. flabellaris.
Ponds, shallow streams, shores and wet mud flats, ditches and drained beaver ponds in the lowland, steppe and montane zones; common throughout BC except rare along the coast; amphiberingian, N to AK, YT and NT, E to NF and S to MA, IA, MI, SD, UT, NM, NV and OR; E Asia.
The table below shows the species-specific information calculated from original data (BEC database) provided by the BC Ministry of Forests and Range. (Updated August, 2013)
