Cocklebur is often found in open, disturbed areas, particularly flood-prone areas with good soil moisture. It frequents rugoadsides, railway banks, small streams, and riverbanks, as well as the edges of ponds and freshwater marshes and overgrazed pastures. It does not tolerate shading. Cocklebur grows on a wide range of soils (sands to heavy clays) and available moisture. On rich soils with abundant moisture and little competition from other plants, it grows tall and luxuriant, forming pure stands. In dry, poor soils, plants may grow to only a few centimetres high, persist through drought, and set seed. The ability to grow under a variety of conditions results in a continuous seed supply. Cocklebur withstands partial submergence for six to eight weeks by forming adventitious roots from the submerged portion of the stem. These roots float in water and often get infested with oxygen-producing green algae (Dedogonium) which solves the problem of aeration. (via Bugwood.org)