Cocklebur

If I had to design vegetation for a movie set on an alien planet, I’d take inspiration from this PEI plant: the odd-looking Rough Cocklebur (Xanthium strumarium). 

Cocklebur gets its name from spine-covered fruit (burs) that look a bit like Burdocks but have two distinctive beaks at the end (inset photo). Like Burdock (Arctium minus), Cocklebur’s Velcro-like fruits are distributed by hitch-hiking on animals, including humans. Those burs also float, allowing them to be readily spread by water. 

As an annual plant, Cocklebur’s high seed production – thousands per plant – is critical to its survival. Add that to those effective seed-distribution systems and you have the recipe for a highly successful plant: Cocklebur is found on every continent except Antarctica. Its global distribution and preference for disturbed habitats have made determining the native range of Cocklebur difficult, but it’s currently considered native to North America, including PEI. 

Here on the Island, Cocklebur is usually a plant of sandy or muddy coastal areas, and I see it mostly along the South shore. That’s good news for Island farmers, as elsewhere in Canada this plant is a serious agricultural pest. In addition to clinging onto livestock (and being a particular problem in wool), Cocklebur is a weed in soybeans and corn and its seeds and seedlings are toxic to livestock, pets, and people (more on this in a moment). 

Toxic plants often have medicinal uses, and Cocklebur is no exception. Its root was used traditionally to treat a wide range of conditions from headaches and allergies to kidney disease, rheumatoid arthritis, and leprosy. The species name ‘strumarium’ comes from its use in treating struma, a swelling of lymph glands in the neck associated with tuberculosis. 

Modern research has identified more than 170 different chemicals in Cocklebur, many having functions that support those traditional uses. Cocklebur components have been shown to have pain relieving, anti-allergy, anti-inflammatory, antifungal, antiviral, antibiotic, anti-arthritic, and antioxidant properties. Extracts from this plant are showing promise in treating several types of cancer. 

Despite its useful properties, this is not a plant for home use. Around the world, consumption of Cocklebur has led to many confirmed fatalities, and there are likely far more that were never reported. Seeds and seedlings contain a chemical called carboxyatractyloside which causes severe liver and kidney damage; mature plants contain several other biochemicals that are known to be toxic (albeit less so than carboxyatractyloside). 

Cocklebur numbers at any one site can vary greatly from year to year, and it’s not unusual for it to be abundant one year and almost absent next. Those spiny burs can hang onto the plant well into fall and winter, so you may still spot them as you explore PEI Untamed!