It is native to much of the Americas from Canada to Chile, and it can be found on other continents as an introduced species.

[4][5] It grows in wet habitat, such as riverbanks, pond margins, and meadows.

It is an annual herb growing a mostly erect, branching stem to exceed 30 centimeters in height.

The oppositely arranged leaves vary in size and shape, from lance-shaped to oval, toothed or not, and under one to over three centimeters long.

It is most notable for having the tiniest seeds of any dicot species; 137,000,000 per pound, or 8,562,500 per ounce.