A summer annual that grows from seed, or may produce shoots and roots at stem joints that lie in the water. Seed production per plant may be heavy, and seeds may remain viable in the soil for up to 6 years. Seeds germinate in early spring, usually the first year. If top portion of plant is cut off it stimulates production of additional flowering stems from the lower parts of the stem. In highly fertile soils stems are thicker and more multi-branched.
Smartweed prefers disturbed areas and low competition from other plants. Generally requires high moisture, and is most likely to be found in aquatic to semi-aquatic conditions – shorelines, ditches, and irrigated fields. In dry or drought conditions the plants are stunted, seed production declines, and many seeds are sterile.