General: Aquatic to amphibious, perennial herb, rooting from nodes of lower stems, roots fibrous, slender; stems coarse, freely-branched, floating or creeping, smooth, hollow.
Leaves: Basal leaves rarely present; submerged stem leaves alternate, semicircular to kidney-shaped, 1-7 cm long, 2-11 cm wide, 1- to 6-times parted, lobed, or dissected, the segments entire or round-toothed, tips rounded to thread-like; floating stem leaves absent or unlike submerged, 3-lobed, lobes linear to oblong; stalks 0.5-4 cm long.
Flowers: Inflorescence of 1- to few-flowered terminal and axillary cymes, on stout stalks to 10 cm long; receptacle sparsely stiff-hairy; petals 5-6, distinct, yellow, 7-12 mm long, 5-9 mm wide, nectary on upper surface, the nectary scale variable, 1.5 mm long; sepals 5, spreading or weakly bent back, early deciduous, 5-7 mm long, 3-6 mm wide, smooth; stamens 30-70; pistils 30-70.
Fruits: Achenes, numerous in an egg-shaped head 8-10 mm long, 7-8 mm wide, the achenes egg-shaped, flattened, 1.8-2.2 mm long, 1.6-2.2 mm wide, smooth; beaks persistent, lanceolate, flattened, straight or somewhat curved at tip, 1-1.8 mm long.
Notes: This species is closely related to R. gmelinii.
Ponds and shorelines in the steppe, montane and subalpine zones; infrequent and scattered in S BC east of the Coast-Cascade Mountains; E to PQ and NB and S to KS, NC, LA, UT, NV and N CA.
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)
