Xanthium spinosum is an 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 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.
- Jepson Manual Treatment of Xanthium spinosum — invasive plant species.
- Pacific Island Ecosystems at Risk — invasive plant species.
- University of California, Calphotos Photo gallery — invasive plant species.
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