Species specifics: Common cocklebur

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Fast facts about common cocklebur

A common native annual weed found throughout much of the United States and credited as one of the most troublesome weeds in agriculture.
Seedlings and seeds are highly toxic and lethal to livestock when consumed at levels equivalent to 1% of body weight.
Known for its 1-inch seeds contained in woody burs that readily attach to many hosts, including clothing and animals.

What to look for

Common cocklebur (Xanthium strumarium) is a toxic annual bushy weed known for its prickly burs that easily attach to animals, clothing and hair.

Common cocklebur seedlings have purple stems with large, shiny, waxy, bright-green leaves that tend to emerge in late spring but have also shown up as late as early summer in some parts of the country. The early leaves appear in an opposite pattern. Adult cocklebur plants can grow up to 4 feet tall with thick branching stems that have purple or black spots and will establish a deep taproot that can be as deep as the plant is tall. As the toothed leaves mature, they can become triangular or more lobed, maintaining a rough appearance throughout their lifecycle. The leaves are also known for having a distinctive smell when rubbed or crushed.

As a summer annual, the weed will typically flower sometime between July and October, with the specific timing dependent on the climate and the weather in any given year. Inconspicuous clusters of small green to rusty red male flower heads develop at the leaf axils in the branched canopy of the plant, and female flowers develop below the male flower heads in oval-shaped fruits with short stalks. The female fruit turns into burs that readily attach to animals, clothing and hair thanks to their spiny exteriors that turn woody and brown once detached from the plant – the highly effective attachment mechanism also serving as the product inspiration for Velcro.

The egg-shaped spiny burs, averaging 1 inch in length, contain two seeds each and can be carried far and wide, which contributes to its affinity for infesting entire pastures in what can feel like a blink of an eye.

The seeds and seedlings of a cocklebur are extremely toxic and can kill livestock if consumed in amounts of at least 1% of their bodyweight.While the entire plant is toxic, the mature plants are typically unpalatable, and animals will generally avoid it in grazing pastures.

Where it is found

Cockleburs are particularly prominent in open, moist areas. However, they are opportunistic weeds that will establish in a variety of soil types and conditions, especially if areas are disturbed.

As a native annual, and often credited as one of the most troublesome weeds in various agricultural systems, the weed is found in more than 46 states, with many states classifying it as a noxious weed.

How to treat it

Apply 16 to 20 fluid ounces per acre of DuraCor® herbicide or 20 to 32 fluid ounces per acre of GrazonPD3™ herbicide. For non-residual weed control, apply 16 to 24 fluid ounces per acre of PastureGard® HL herbicide or 24 fluid ounces per acre of NovaGraz™ herbicide plus 1% MSO v/v. Use lower rates when weeds are small and actively growing and increase rates as the season progresses and plants become more mature.

Herbicide-resistant common cocklebur has been recorded in 12 states, including Kansas, Illinois, Iowa, Missouri and Ohio, with populations showing resistance to ALS-inhibiting herbicides. For questions about how to best handle cocklebur in your area, reach out to your local Range & Pasture Specialist.

GrazonPD3™ is a Restricted Use Pesticide. GrazonPD3 is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. GrazonPD3 is not for sale, distribution or use in Nassau and Suffolk Counties in New York State. Under normal field conditions DuraCor® is non-volatile. DuraCor has no grazing or haying restrictions for any class of livestock, including lactating dairy cows, horses (including lactating mares) and meat animals prior to slaughter. Label precautions apply to forage treated with DuraCor and to manure and urine from animals that have consumed treated forage. DuraCor is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. PastureGard® HL herbicide is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. When using NovaGraz™ herbicide, white clover and annual lespedeza exhibit some initial injury (such as lodging and loss of vigor) but recover. NovaGraz™ is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.