Stems usually densely villous, rarely sparsely so, hairs often viscid when fresh, or glabrate on submerged stems. Leaves alternate, sometimes fascicled; stipules often asymmetrical; petioles of basal leaves (0.5–)0.8–1.6 cm, those of distal leaves 0.5–2.8 cm; blade (0.4–)1–6(–9.5) cm, apex glandular-mucronate, surfaces not shiny, usually densely hirtellous, rarely glabrous abax­ially. Flowers: anthers on short filaments (0.7–)0.9–1.8 mm, those on long filaments (0.8–)1.1–2.2 mm; ovary 6–10 mm, apex truncate, densely hirtellous, some­times only on apical 1/2, stigma usually as long as anthers, rarely exserted beyond them. Capsules (20–)24–32 × 2–4 mm, pedicel 7–38(–60) mm. Seeds 10–15 per locule. 2n = 16 (32).

Phenology: Flowering summer-early fall.
Habitat: Wet places, along slow-moving rivers, streams, canals, ditches, often growing into main channels as aquatic weeds.
Elevation: 0–500[–2000] m.

Distribution

• Generated Map
• Legacy Map

Introduced; Calif., La., South America (Argentina, Brazil, Chile, Peru, Uruguay), introduced also in Europe (France), Pacific Islands (New Zealand), Australia.

Discussion

In the flora area, subsp. montevidensis is introduced in California (P. H. Raven 1963c), where it was first collected in 1906 (El Dorado County, Rixford s.n., CAS), and in Louisiana. Subspecies montevidensis occasionally forms masses of vegetation that can obstruct water flow and navigation in California and elsewhere.

Selected References

None.

Lower Taxa

None.