Scientific name: Xanthium cavanillesii, X. spinosum (Asteraceae)

Common name: carrapicho-de-carneiro, carrapichao, espinho-de-carneiro, figo bravo

Description: Xanthium is a spreading herbaceous annual approximately 1.5m in height found in frequently or periodically flooded areas. The leaves have 3-5 lobes per leaf and the leaf margin is serrate. The plant germinates in spring and early summer with flowering in the fall. Flowers are inconspicuous and there are 2 types. Male flowers occur on short terminal branches. Female flowers, which produce the seed, are found in clusters in the axils of the leaves. The fruit is a hard, 2-chambered bur, oval, green and becoming maroon and dry when mature. It contains 2 seeds. One seed germinates immediately and the other may remain dormant for months or years before germinating. The fruits float and are easily dispersed during flooding. Additionally the burs on the fruit may become entangled in animals' coats and are difficult to remove, reducing the value of wool.

The seedlings appear 4-14 days after flood waters recede. The seeds and cotyledons (seed leaves) are the most toxic components of the plants. The seedling consists of a slender, straight whitish green stem 2-6cm tall. At the apex of the stem are two strap-shaped green seed leaves, each about 2.5cm long and 0.5cm wide. As the seedling grows the plant becomes less toxic.

Xanthium spp. are highly invasive in cultivated crops and as a result their seeds may appear in feeds due to mechanical harvesting practices.