I was walking around in the brush recently and noticed thick stands of cockleburs (Xanthium sp.). I tried to avoid them, but before I realized it my pants collected dozens.

People with hunting dogs know all about cockleburs. Long-haired dogs have even more problems. Sometimes prickly burs get so entangled that cutting them out is the only option.

I remember putting up hay and coming home with my fingers full of pieces of these nasty briers. I also recall spending hours removing them from an old collie mutt.

Unfortunately, the discomfort of sandwiching one of these burs in between the skin and another object is not the worst of the problem. The cocklebur plant is poisonous. They are a major problem in crop and pastureland.

Toxicity to animals can occur at different times of the year, but newly emerged seedlings are the biggest concern. Early spring is a problem time in pastures. Sometimes animals can get poisoned later in the year when mature seeds drop and start to grow.

Seeds are toxic too. I don’t know of anyone who would try to eat these spiny things, but pets and livestock might ingest some while trying to groom themselves.

Toxicity is caused by Carboxyactractyloside or CAT for short. CAT interferes with cellular energy exchange. It’s a little complicated, but the bottom line is that even low levels of the compound can cause death. This chemical is not a problem in mature plant tissue.

When I lived in West Virginia I don’t recall many toxicity problems with cockleburs. My in-laws never had any poisonings from cocklebur and their neighbors didn’t either. These weeds were more of a nuisance than anything.

I think there were three primary reasons for this. First, their cattle were never lacking for hay in winter. This meant that the animals had the luxury to eat around the spiny burs and not ingest the seeds.

Another reason was probably because most farmers tried to wait until pasture growth was well established in spring before stocking animals. Placing livestock on them before adequate forage accumulated meant short thin pastures during the summer heat.

Finally, cattle were never allowed on meadows until it was time to feed hay. This meant any cocklebur seeds that germinated were already too mature to cause problems.

Cocklebur is an annual weed and spreads only by seed. Clipping pastures before seeds mature can help eliminate the spread of this weed. Many herbicides can control it, but they might leave residues that could accumulate in livestock.

This is a lesser problem in corn and soybeans as there is normally a longer time period between chemical application and harvest. It is impractical to keep animals from grazing an area for much of the growing season.

Cockleburs are problematic for pets. I doubt dogs would deliberately eat them, but they could ingest seeds by trying to remove the burs with their teeth, That’s the only way they know how. They also can get burs stuck in their tongues. Therefore, I suggest grooming your dog if they bring home a coat full of cockleburs.

Cocklebur plant in late winter

Cockleburs on my jeans

Cockleburs on my coat

Close-up of the burs

Ted Manzer teaches agriculture at Northeastern High School (tmanzer@ecpps.k12.nc.us).