Scientific name

Xanthium strumariumL.

Synonyms

Xanthium americanum Walter; Xanthium canadense Mill.; Xanthium occidentale Bertol.; Xanthium pungens Wallr.; Xanthium chinenseMill.

Common names

Large cocklebur, Canada cocklebur, cocklebur, rough cocklebur, common cocklebur

Family

Asteraceae

Origin

Uncertain, suspected to be Central and South America although it was first described from Europe.

Naturalised distribution (global)

Xanthium strumarium is widely naturalised between latitude 53°N to 33°S, where it is most common in the temperate zone, but is also found in subtropical and Mediterranean climates.

Introduced, naturalised or invasive in East Africa

Xanthium strumarium is considered to be invasive in parts of Kenya, Uganda and Tanzania (A.B.R. Witt pers. obs.). In Kenya, this plant has been recorded in Samburu, Rift Valley, Nairobi and Bungoma, Kakamega, Kisumu, Kisii, Tsavo National Park and Meru National Park. In Tanzania, this species is found in Moshi, Lushoto, Kasulu, Central highlands, Morogoro, Rugwe, and Iringa. In Uganda it is also likely to be widespread.

Habitat

Xanthium strumarium invades farmland, old lands, roadsides, wastelands, riverbanks and overgrazed pasturelands. It is considered a ruderal weed of maize farms in Western Kenya.

Description

Xanthium strumarium is a much branched annual up to 1.2 m high. It has stout stems, green, brownish or reddish-brown in colour, often red-spotted that are rough and hairy.

The leaves are alternate, dull green on the upper surface and paler below, with short bristly hairs on both surfaces. They are broad, and 3-5 lobed, 30-180 mm long by 30-180 mm wide on long petioles (stalks).

X. strumarium flowers are yellowish green,  located in special, almost spherical apical capitula, inconspicuous, in the leaf axils. The corolla is true, tubular; stamens free. The involucre upon fruiting turns into dense ligneous prickly pericarp.

The fruit is called a bur, its ovoid (oval shaped) and it measures about 1.3-3.5 mm long, green, turning yellow and then brown in stalked axillary clusters. Each bur has two stout, curved or straight horns and is covered with hooked spines.

Reproduction and dispersal

The seeds are dispersed through contaminated farm tools, waste soils and furry farm animals. In western Kenya, oxen often carry masses of the spiny fruits on their fur, from invaded farms during the ploughing season.

Economic and other uses

Xanthium strumarium can be used as a medicinal plant. A yellow dye can be made from its leaves. However, these uses cannot compensate for its overall negative impacts.

Environmental and other impacts

Xanthium strumarium is a major weed of row crops such as maize, groundnuts, cotton and soya beans. It can also invade pastures and grazing lands causing reductions in forage production. It is toxic to most domestic animals.

Xanthium strumarium has been listed as a noxious weed in South Africa (prohibited plants that must be controlled. They serve no economic purpose and possess characteristics that are harmful to humans, animals or the environment).

Management

The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are introduced below.

The best form of invasive species management is prevention. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.

All control efforts should be aimed at preventing seed formation. Single plants and small infestations can be hoed and larger infestations sprayed with herbicide.  When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

A range of biological control agents have been targeted at this species but with variable success (CABI IAS Compendium).

Legislation

Not listed as a noxious weed by the state or governments in Kenya, Tanzania and Uganda.

References

Agnew, A. D. Q. and Agnew, S. (1994). Upland Kenya Wild Flowers. A flora of the Ferns and Herbaceous Flowering Plants of Upland Kenya. 2nd Ed. EANHS, Nairobi-Kenya.

BugwoodWiki online data sheet. Xanthium strumarium. http://wiki.bugwood.org/. Accessed 13th March 2011.

CABI Invasive Species Compendium online data sheet. Xanthium strumarium (common cocklebur). CABI Publishing 2011. http://www.cabi.org/ISC. Accessed 13th March 2011.

Henderson, L. (2001). Alien Weeds and Invasive Plants. Plant Protection Research Institute, Agricultural Research Council, South Africa.

Editors

Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.

Acknowledgments

This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: [email protected]