To make a homemade dandelion killer, mix together 1 gallon of household vinegar and 1 ounce of liquid dish soap in a large container. You can add lemon to make the solution more potent, and you may want to consider a biodegradable dish soap. You may need a pump sprayer to dispense the solution adequately.

  1. Create the mixture

    Pour 1 gallon of vinegar into a container. Add 1 ounce of dish soap to help the solution stick to the leaves. Mix together thoroughly to avoid creating bubbles.

  2. Clean the sprayer

    Remove any residue from the pump sprayer before pouring in the solution. Pour in 1 quart or less of the mixture. Use a smaller sprayer for more control when spraying. Pump the sprayer when the solution is inside.

  3. Apply the weed killer

    Spray the solution on the leaves and flower head of the dandelions during the hottest part of the day so that the sun can help the vinegar drain moisture from the plants. Make certain that all of the plant is thoroughly coated, and take caution when spraying the area. Wait anywhere from 24 to 48 hours to see if the plants are wilted and brown. Apply the solution every three days for resistant weeds. Store the remainder of the weed killer in a cool location that doesn't receive sunlight.