Homemade Weed Killer – Will It Hurt My Trees?

Q: I am using a mixture of vinegar and salt and detergent to kill weeds. Will it hurt the mature oak, magnolia, or pine trees in my yard? 

A: Philippus Aureolus Theophrastus Bombastus von Hohenheim (known as Paracelsus by his friends) is considered by some as “the father of modern medicine.” One of Paracelsus’ key observations was that “The dose makes the poison.” In other words, a substance that is harmless in small amounts can be poisonous in large doses. Whether your trees will be hurt depends on how much of your concoction soaks into the soil. If you just spray it on the weed leaves I don’t think there is any danger to the trees. In my experience, your mixture is not dangerous to most weeds either. Commercial herbicidal soap works better.