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Termites | The wild thing for the week of 6/23/08
Common cocklebur, Xanthium strumarium, is a poisonous annual broadleaf weed with ferocious burs. It can be found in fields, pastures, roadsides and gardens that receive full sun.
Common cocklebur can be identified by its rough-textured stem. The stem is erect, reaches up to 4 feet in height and has distinct dark purple spots. The leaves have a coarse sandpaper texture, are often lobed, and have coarse teeth along the margins. The leaves also have long petioles.
When the seedling emerges, it may still have the bur attached to the top. The cotyledons are thick and fleshy. The first true leaves are opposite. Early leaves are triangular and have three distinct veins. Later leaves are alternate.
Egg-shaped burs with hooked spines form in summer and each bur contains two seeds -- one is ready to germinate and one remains dormant for a time.
The entire plant is toxic; however, young seedlings and seed contain the largest amounts of toxin. Symptoms vary because the plant has several toxins including carboxyatractyloside and a group of sesquiterpene lactones. Liver damage can occur and animals can die if they ingest as little as 1 percent of body weight. Pigs are particularly susceptible to the toxins found in seedlings. The spiny seed bur also causes internal injury.