Spiny Cocklebur (Xanthium spinosum L.)

Family: Asteraceae

Description and Variation: Spiny cocklebur is an erect, much branched annual that grows up to three feet high. It reproduces by seed. About one inch long spines are found in leaf axils and at stem nodes. The leaves are shiny dark green and hairy on the upper surface and downy beneath. The leaves are mostly three-lobed with the center lobe  much longer than the other two, and up to three inches long. The flowers are small, inconspicuous, and creamy green. The male flowers are found at the top of the stems and the female flowers are formed lower on the stems. The fruit is more or less an egg-shaped burr, up to one-half inch long, armed with numerous hooked spines, some with one or two straight terminal spines. There are two seeds per burr, flattened, three-eighths inch long and brown in color.

Economic Importance: Detrimental: The burrs of spiny cockelbur can become tangled in the hide of cattle and horses and in the wool of sheep. Removal of the burrs from wool adds to the cost of the final woolen product. Spiny cocklebur can provide some competition for summer crops and is a nuisance to pickers in hand-harvested crops. The seeds and cotyledonary seedlings are poisonous. Ingestion of seeds equal to 0.3 percent of the animals weight, or ingestion of seedlings equal to 1.5 percent of the animal’s weight are toxic. Poisoning has occurred in all classes of domestic livestock, and is always associated with cotyledonary seedling ingestion. The symptoms are anorexia, depression, nausea, and prostration. Death may occur in a few hours to three days after the symptoms are first noted.  

Beneficial: Compounds from spiny cocklebur may have pharmaceutical value as diuretics.

Habitat: Spiny cocklebur is adapted to a variety of climates, hence its wide distribution. It is found in a wide variety of soil types growing in cultivated fields, wastelands, farm yards, flood plains, and along waterways.

Geographic Distribution: Spiny cocklebur is native to Chile. It is now widespread in the warm and temperate regions of the world, occurring commonly in Europe, Asia, North and South Africa, North and South America, and Australia.

History: Spiny cocklebur was introduced into the United States from South America. It was probably brought in as burrs attached to livestock. It has since spread along the east and west coasts and the Gulf coast.

Growth and Development: Morphology - the numerous hooked spines of the fruit enable it to adhere to animals and be transported long distances. Perennation - Overwintering occurs in the seed stage. Phenology - The seeds germinate after late spring and summer rains, or irrigation and the young plants grow quickly. The plants flower in summer and bear fruit until killed by fall frosts.

Reproduction: Spiny cockelbur reproduces by seeds only. Seed Production and Dispersal - The seeds are well adapted for dispersal by livestock or people because of the hooked spines on the fruit. Viability of Seeds and Germination - Of the two seeds in each burr, one germinates the first spring or summer and the other does not germinate until the second or third year. Some seeds may remain viable for up to eight years. Population Dynamics - Spiny cocklebur can spread rapidly to infest new areas because of its ability to be spread by livestock. The plant may persist in an area for a long time due to the long-lived seeds in the soil.

Response to Cultural Methods: On arable land, cultivation is effective against the seedlings. This should be repeated periodically for at least three years. Mowing or slashing are effective if done prior to burr formation.

References:

Holm, L.G., and D.L. Plucknett, J.V. Pancho, and J.P. Herberger. The World’s Worst Weeds. East-West Center Food Institute. University Press of Hawaii.

Kingsbury, J.M. 1964. Poisonous Plants of the United States and Canada. Prentice-Hall, Inc. NJ, 626 p.

Lange, A.H. and B.B. Fischer. 1978. Grower’s Weed ID Handbook. University of California Ag. Extension Service.

Mitich, L.W. 1981. The Intriguing World of Weeds, Part XI. Weeds Today 12(4):11.

Parsons, W.T. 1981. Noxious Weeds of Victoria. Inkata press, Melbourne, Australia. 300 p.

This page was last updated 03/31/07