Is Herbicidal Soap The Same As Dawn Dish Detergent?

Q: Last week, you recommended spraying herbicidal soap on weeds in an asparagus bed. Is this the same as Dawn dish detergent?

A: Absolutely not! Dawn is a detergent, not a soap. Although both dissolve fat and wax, a detergent works more as a binder, preventing fats and waxes from reattaching to your dishes. Herbicidal soap is a specific mix of ammoniated fatty acids. You could wash your hands with it if you like, but it’s better used to kill weeds. It dissolves the wax on plant leaves and they dry out and die. It is a nonselective weed killer. I recognize that herbicidal soap is somewhat hard to find. Here are some brand names to look for online: Weed-Aside, Finalsan, and Monterey Herbicidal Soap.

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