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| Native Distribution | Tropical & Subtropical Americas (e.g., Argentina to N. Carolina, USA); naturalized in tropical Africa, Australia, coastal Brazil. | Americas (North, Central, South, e.g., USA to Brazil, Chile); naturalized in New Zealand, Thailand, parts of Africa. | North & South America (USA to Argentina/Chile), Australia, South Africa, tropical/subtropical Africa (e.g., Somalia to South Africa). |
| Habitat | Sandy/skeletal soils, brackish coastal areas, sand dunes, inland damp places, lawns/gardens; tolerates dry/flooded extremes, submaritime (0-50 m elevation). | Moist/wet areas: marshes, river/lake shores, wetlands, riparian zones, swamps, roadside ditches, maritime grasslands; prefers high water fluctuation sites. | Marshy/boggy/wet depressions, pond margins, shallow river/lake edges, wet littoral; versatile in waterlogged, submerged, or terrestrial conditions. |
| Growth Habit | Perennial rhizomatous herb, creeping/prostrate stems rooting at nodes; glabrous, emits strong odor when crushed. | Perennial herb, floating/creeping/slightly succulent stems, stolons; forms dense mats. | Perennial herb, creeping stems up to 30 cm, rooting at nodes; glabrous, adaptable to varying water levels. |
| Leaf Morphology | Round, peltate, large (4-15 cm wide), crenate/lobed margins; blade held vertically; abaxial surface visible. | Round, peltate, 0.5-7.5 cm diameter, crenate/slightly lobed; coin-like, held horizontally. | Round, peltate without sinus/notch, smaller (2-4 cm diameter); alternate along stem. |
| Flower Morphology | White to creamy-yellow, in numerous umbels; stalks up to 30 cm tall; flowering Apr-Aug (–Nov). | Small white/greenish/yellowish, in simple umbels (10-60 flowers); flowering Apr-Oct. | Small/inconspicuous white, in whorls (verticils) forming interrupted spike/raceme; flowering May-Aug. |
| Fruit | Small, ellipsoid; seed dispersal via water/animals. | Ellipsoid, small; long-lived seed bank. | Small, inconspicuous; dispersal by seed/stem fragments. |
| Other Notes | Often a weed in coastal regions; C3 photosynthesis; medicinal potential (e.g., functional food). | Edible (leaves in salads), medicinal (e.g., cough treatment), invasive potential, phytoremediation uses; larger than similar species. | Popular in aquaria (undemanding, good substrate needed); thrives submerged/emersed; distinguished by whorled flowers and unnotched leaves. |