Want to reduce your exposure to toxic weed-killing yard chemicals? Researchers have found treatments using boiling water, steam or fire will dispatch even the hardiest of unwanted weeds from between paving stones as effectively as chemical spray weed-killers.
The study, by University of Copenhagen scientists, found six successive heat treatments will kill weeds completely.
But the treatments need to be administered correctly so that every single plant is burned lightly – or blanched – and the leaves wilt completely.
"We have observed that the treatments work,” said lead researcher Anne Merete Rask. “It does not really matter whether you use flaming, steam or boiling water. However, if we only give a few treatments or if we use low doses, the weeds quickly reappear. Very low doses can even stimulate grass growth. This is also the case with many herbicides."
Rask said repeated treatments ensure the “weed is starved” and the leaves collapse after each one.
“The leaves must wilt completely after each treatment,” she said. “This prevents the plants from storing carbohydrates in their roots, which is necessary for regrowth."