The cockle-burr or cocklebur plant (Xanthium strumarium) earns its name from the shape and texture of its seedpods. Each tiny pod resembles a cockleshell of spiny burs. The plant's genus name, Xanthium, is derived from the Greek word for "rough," and its species name, strumarium, translates to "cushionlike swelling." The spiny, oval burs reach a length of 1 inch and resemble burdock burs. Each holds two black or brown seeds. Cocklebur is considered an invasive weed because it poses problem for humans and animals.
The cocklebur can be found almost worldwide between the latitudes of 53 degrees north and 33 degrees south. It lives throughout most of the contiguous United States, Mexico and southern Canada. The only U.S. locations where cocklebur does not grow are northeastern New York and Maine. Typically, it does not grow in mountain areas.
Cocklebur grows in disturbed soil across the United States. It is commonly found in cornfields, open pastures and ditches, along roadsides and in other open areas. Because cockbur seeds survive in soil for months or even years before germination, the plants may appear in newly disturbed soil when conditions favor the seeds' germination. Seeds are dispersed by animals after the burs attach to their fur and are carried to new areas.
Cocklebur seeds need moist soil to germinate, making cocklebur plants common in wet areas such as ditches, stream banks, the bottoms of dried bodies of water and areas where soil floods in spring. The seeds may suddenly germinate when exposed to moisture, or they may be washed into those area via flood waters. In dry locations, cocklebur may be found near water holes or near irrigated land. Cocklebur is not fussy about soil pH or soil fertility, growing in poor soil.
Sunlight Requirement and Weather Effect
Cocklebur performs best when exposed to full sun for at least six hours each day, making this plant a common sight in sunny locations. Although its seeds typically germinate in spring, seedlings may emerge during summer after heavy rains cause dormant seeds to sprout.
Cocklebur can be an invasive weed that takes over an area, crowding out other plants. Because it grows to a height of 5 feet, it may shade out smaller plants. When the plant produces burs, those burs can become a nuisance to livestock, household pets and humans because they cling to fur and clothing. In addition, young cocklebur seeds and seedlings are toxic to animals and humans and may pose a risk to their health and safety.