Jacobaea vulgaris is a devious weed known in agricultural circles as ragwort. When mature, ragwort resembles a tall dandelion, with a bright yellow flower featuring long thin petals. Farmers have been trying to eradicate ragwort for years, and at one point in 1930s New Zealand, the war on ragwort became dangerous — to the dairy farmers trying to spray it away.
New Zealand’s Department of Agriculture had recommended using a herbicide called sodium chlorate, and it was effective against ragwort. The downside was that when dry, the chemical became highly caustic. Many farmers found this out the hard way when their pants began to explode, sometimes leading to injuries.
Scientists eventually discovered that the herbicide — sodium chlorate powder mixed with water — became flammable when the water evaporated, leaving tiny crystals embedded in the fibers of the farmers’ denim jeans,.
The curious case of the exploding trousers:
One farmer made the local news after his pants exploded. He’d hung up the wet trousers next to the fire to dry, and before long the pants burst into flames.
Other farmers suffered severe burns when their pants literally ignited — while they were still wearing them.
Ragwort is poisonous to horses and cows, making it unacceptable ground cover in grazing pastures. The stomachs of sheep and goats can tolerate ragwort, and those animals are now used to try to keep the weed from growing out of control.