Certified Organic Natural Non-selective Herbicide. Weed Zap is an all natural non-selective herbicide. Weed Zap “zaps” small broadleaf and grassy weeds. Its natural ingredients will control plants that are 6 inches in height or less. Weed Zap is a broad spectrum herbicide that is often used in commercial organic production. 1 gallon concentrate makes 20 gallons of solution.