Xanthium canadense Mill.
Xanthium strumarium (rough cocklebur, clotbur, common cocklebur, large cocklebur, woolgarie bur) is a species of annual plants of the family Asteraceae. It probably originates in North America and has been extensively naturalized elsewhere.
The species is monoecious, with the flowers borne in separate unisexual heads: staminate (male) heads situated above the pistillate (female) heads in the inflorescence. The pistillate heads consist of two pistillate flowers surrounded by a spiny involucre. Upon fruiting, these two flowers ripen into two brown to black achenes and they are completely enveloped by the involucre, which becomes a bur. The bur, being buoyant, easily disperses in the water for plants growing along waterways. However, the bur, with its hooked projections, is obviously adapted to dispersal via mammals by becoming entangled in their hair. Once dispersed and deposited on the ground, typically one of the seeds germinates and the plants grows out of the bur.
Toxic or medicinal phytochemistry
However, while small quantities of parts of the mature plants may be consumed, the seeds and seedlings should not be eaten in large quantities because they contain significant concentrations of the extremely toxic chemical carboxyatratyloside. The mature plant also contains at least four other toxins.
- Animals have also been known to die after eating the plants.
- A patient consuming a traditional Chinese medicine containing cocklebur called Cang Er Zi Wan (苍耳子丸) developed muscle spasms.
- It was responsible for at least 19 deaths and 76 illnesses in Sylhet District, Bangladesh, 2007. People ate large amounts of the plants, locally called ghagra shak, because they were starving during a monsoon flood and no other plants were available. The symptoms included vomiting and altered mental states, followed by unconsciousness.
Use by Native Americans
The Zuni people use the canadense variety for multiple purposes. The chewed seeds are rubbed onto the body before the cactus ceremony to protect it from spines. A compound poultice of seeds is applied to wounds or used to remove splinters. The seeds are also ground, mixed with cornmeal, made into cakes, and steamed for food.
Xanthium strumarium – MHNT
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