Vinegar-based pesticides can be effective against weeds; however, store-bought vinegar is not powerful enough to have an effect. Horticultural vinegar pesticides contain at least 20% acetic acid, while grocery store products only have 5%.
This stronger concentration can kill weeds in as little as 24 hours, but it only eliminates above-ground growth. The root system is left unaffected, allowing weeds to grow back. Vinegar is also non-selective, meaning it will harm your grass, flower, shrubs, and trees if they are accidentally sprayed.