Add 1 tsp. of liquid food coloring to 1 cup of water. Drizzle the colored water onto the soil surrounding the base of a plant. Wait 24 hours for the water to absorb. Apply another identical dose if the color change was not sufficient.
Natural Weed Killer 1 gallon vinegar, 1/2 cup salt, dash of dish washing detergent (makes it stick to the weeds). Mix well, spray on weeds in the morning, rejoice in their death that evening. This works best on a sunny day.