Express.co.uk tested four natural weed killers on patio weeds: rock salt, white vinegar, lemon juice, and boiling water. Two methods—rock salt with boiling water and white vinegar with dish soap—killed weeds within 24 hours. Lemon juice and boiling water alone were ineffective.
Rock Salt and Boiling Water: Effective in Under 24 Hours
Angela Patrone tested rock salt on broadleaf and crabgrass weeds on block paving. She sprinkled salt directly on weeds, then poured boiling water over them. Within an hour, leaves and stems wilted and turned brown. After nine hours, the weeds died completely and were easily removed with a screwdriver. No regrowth appeared after two weeks.
According to Chelsey at Good Grow, the "easiest, fastest and best way" is to sprinkle salt before pouring boiling water. Boiling water helps dissolve salt and scalds weeds. Salt dehydrates the weed, acting as a contact herbicide.
White Vinegar and Dish Soap: Quick Results
Phoebe Cornish tested white vinegar mixed with dish soap following Martha Stewart's recommendation. She combined just under 500ml of distilled white vinegar with a quarter teaspoon of Fairy Liquid in a spray bottle. Applied to weeds on a dry, muggy day after rain, the weeds appeared pale and withered within a few hours. The next morning, they were significantly weakened and easier to pull out by the root.
Craig Elworthy, founder of Lawnbright, advises: "Allow the vinegar weed killer to sit on the weeds for several hours or overnight. You should notice a big difference by the next day." The acetic acid in vinegar destroys weed tissue on contact, but does not kill roots.
Lemon Juice: Ineffective
Ketsuda Phoutinane applied juice from three lemons (about 100ml) to weeds between paving slabs. After 24 hours, the weeds appeared to have flourished. Rain may have washed away the juice, but the method failed under the test conditions.
Boiling Water Alone: Not Enough for Established Weeds
Sophie Law poured boiling water directly onto a dandelion in gravel. The leaves and flower wilted immediately, but after 24 hours the dandelion was still alive. Boiling water alone struggles to kill deep-rooted established weeds. It works best on small, recently emerged weeds, but may require repeated applications.
Boiling water is safe, eco-friendly, and free, but not as effective as salt or vinegar methods for mature weeds.
