Boron concentrations in streams, swamps, ponds and reservoirs of the southeastern United States were usually below 100 ppb. Levels of boron in rainfall varied greatly between different periods of precipitation, but the highest concentrations were observed during winter. However, most rainfall samples contained less than 10 ppb boron. The annual input of boron in rainfall at two Mississippi sites and one station in South Carolina ranged from 62.7 to 74.2 g/ha. Boron levels in 22 species of aquatic macrophytes from a reservoir ranged from 1.2 to 11.3 ppm dry weight. The plant population accrued from 0.5 to 6.8 mg boron per sq. m. Boron uptake studies on Typha latifolia populations indicated a maximum rate of uptake during early spring growth. Boron concentrations in T. latifolia and Juncus effusus samples from different sites varied considerably. There was no significant correlation between concentrations of boron in soils and in plant tissues. Standing crops of T. latifolia increased with increasing levels of soil boron.