The smooth burr marigold (Bidens laevis (L.) BSP) is an annual, native to North American wetlands ranging from southern New Hampshire to Florida and across to California. In Florida, the plants grow in saturated or inundated soils and are perennial where no killing frosts occur. The genus was named Bidens, 'two-toothed' for the two barbed awns of the achenes (hard dry fruits). Each achene holds a single seed.

Burr marigold seeds will germinate either on moist soil or under water. If buried in acidic mucky soils, the seeds go dormant until the soil is disturbed. It appears that seed dormancy is induced by a lack of oxygen (hypoxia). The seeds remain viable and are believed to persist for years.