Dual action formula that kills existing weeds and grasses down to the root. Prevents new weeds from growing for up to 4 months by creating an invisible barrier in the soil. Ideal to use on driveways, sidewalks, patios, around trees, landscaping areas, along fences, and gravel areas. For best results, apply during warm, sunny weather above 60 degrees Fahrenheit. Rainproof in 30 minutes. Visible results in 6 hours.