Xanthium spinosum

Xanthium spinosum is a species of flowering plant in the aster family known by many common names, including spiny cocklebur, prickly burweed and Bathurst burr. It is known worldwide as a noxious weed that grows in many types of disturbed habitat. Its original native range is not known but it may have come from South America, possibly from Chile. This is an annual herb producing a slender stem up to a meter tall or slightly taller. It is lined at intervals with very long, sharp, yellowish spines which may exceed three centimeters in length and may divide into two or three separate spines. The leaves are divided into linear or lance-shaped lobes, the middle much longer than the others, and are arranged alternately all along the stem. Each is up to 10 or 12 centimeters long and dark green or grayish on top with a white underside. The plant produces male and female flower heads, the female heads developing into burs one or 1.5 centimeters long and covered in thin spines. The spiny burs are easily dispersed to new areas when they become attached to animals, people, and objects, or float on water. Bur damage to sheep's wool reduces its value. The plants, especially new seedlings, are toxic to livestock.