Veterinary Medicine Library

Cocklebur (Xanthium strumarium L.)

| Description | Distribution | Conditions of poisoning | Control | Toxic principle | Clinical signs | References



The cocklebur plant is a coarse herbaceous annual about 3 feet high. They have erect, stout stems and spreading branches that are angled and often red-spotted. The leaves are alternate, rough to the touch, and broadly triangular to heart-shaped. Cockleburs produce two kinds of flowers. One kind, in short terminal branches, produces only pollen; the other kind, in clusters in the axils of the leaves, produces seed. The fruit is a small, hard, 2-chambered bur, oval in shape and about 3/4 inch long. It is covered with strong, hooked spines. This plant reproduces only by means of its seed.

Cocklebur seed capsules Cocklebur fruit in early development Cocklebur in late summer
  seed capsules            Early fruit In late summer

The seedling, the plant's most dangerous stage, is very different from the mature plant. It consists of a slender, straight whitish green stem 1 to 3 inches tall. Capping this stem are two strap-shaped green leaves, each about 1 1/4 inches long and l/4 inch wide. Leaves produced after these first leaves gradually assume the characteristic shape of those of the mature plant. Proof of the identity of young seedlings may be found in their attachment underground to the easily recognized burs from which they sprout.


Cockleburs occur throughout Illinois and the rest of the U.S. as stray plants in waste places, cornfields, pastures, and along roadsides, fencerows, stream banks, the beds of dry ponds, and previously flooded land along streams and rivers. Pastures and meadows may be heavily infested, especially with the seedling stage as the result of the burs having been washed in from adjoining fields.

Conditions of poisoning

Pigs rooting and grazing in cocklebur infested places are the most often poisoned domestic species, with those weighing between 20-50 pounds being the most susceptible. Poisoning also affects cattle, sheep, horses, and fowl.

The plant is most hazardous at the seedling stage because of its toxicity as well as palatability. Ingestion of young seedlings in the amount of 0.75% of the animal's weight may result in clinical signs of toxicosis in a few hours and death in 24-48 hours. Approximately 500 seedlings was lethal to a 40-pound pig. The seeds are poisonous at 0.3% of animal weight but are seldom eaten because of their spiny capsule. Occasionally the eating of the ripe spiny capsules is said to result in intestinal obstruction. Mature plants, however, are seldom eaten, perhaps because of their bitterness and rough texture.


Animals should be kept out of infested grazing grounds and drinking places during late spring and early summer when cocklebur seeds are sprouting. Plants in crop fields and pastures may be removed by hoeing and weeding. Heavily infested places should be mowed before the plants form seeds.

Toxic principle

Carboxyatractyloside, a sulfated glycoside, which is present in high concentrations in the seed and cotyledon, is now believed to be the primary toxic principle. As plants develop past the seedling stage, their toxicity decreases. The seeds and seedlings of cockleburs contain the glucoside xanthostrumarin. Toxicity is not lost on drying.

Clinical signs

Clinical signs usually appear within 2-24 hours after ingestion and may be followed by death within 3 days after the onset of illness. Signs most often include anorexia, reduced responsiveness, vomiting, rapid weak pulse, dyspnea, muscular weakness, prostration, and spasmodic contraction of leg and neck muscles. Ascites and potentially lethal hypoglycemia may occur.

Pigs display signs consistent with abdominal pain, and if severely poisoned may show opisthotonos, spasmodic running motions followed by convulsions and death after about 48 hours.

Cattle may become blind, develop extreme hypersensitivity to external stimuli and prominent convulsions. Calves die acutely, often within 12 hours.

Fowl show markedly reduced response to external stimuli which may be followed by death.

Other References:

Cocklebur entry in Wikipedia

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