Xanthium spinosum (also known as Acanthoxanthium spinosum) is a species of flowering plant in the aster family known by many common names, including spiny cocklebur, prickly burweed and Bathurst burr. This species is part of the genus Xanthium that encompasses 25 different species of flowering plants of the daisy family, Asteraceae, and sunflower tribe.
Distribution
It is known worldwide as a noxious weed that grows in many types of disturbed habitats such as pastures, crops, waterways, grasslands, flood plains, waste areas, and sometimes tropical and arid environments. Its original native range is not known but it may have come from South America, possibly from Chile. The plant is found in various regions across the world including Canada, the US, Central America, parts of Africa and the Middle East, China, Russia and Australia.
Description
Burs of Xanthium spinosum
Xanthium spinosum is an upright, highly branched, dichotomous, annual herb producing a slender stem up to 1 metre (3 ft 3 in) tall or slightly taller. It is lined at intervals with very long, sharp, yellowish, three pronged spines which may exceed three centimeters in length. These spines are typically found at the base of each leaf fork.
The leaves are irregularly lobed or lance-shaped lobed, the middle is much longer than the others, and have white veins down the center. They are arranged spirally or alternately along the stem. Each is up to 10 or 12 centimeters long and are dark green or grayish on top, pale green or whitish underneath and are covered in downy hairs.
Xanthium spinosum flowers between summer and late fall, typically from July to October in the northern hemisphere. The plant produces male and female flower heads that are monoecious and form greenish axillary or solitary inflorescence clusters. The male flowers are bulbous and found in dense clusters at the tips of stems near the topmost leaves. Female flowers are found at the leaf forks on lower leaves and develop into...
