The active ingredients in most organic weed killers are acids. These acids work by lowering the pH levels in plants enough to kill them. Consequently, household vinegar is often recommended as the key ingredient for a household weed killer. Vinegar is a strong acid. To be an effective weed killer on any but the youngest, most tender weeds, it must be used at a concentration of 15 to 30 percent. Unfortunately, almost all household vinegar is only 5 percent. Luckily, there is another household product that makes a great weed killer. Bleach, like organic weed killers, also drastically changes the pH of plants. But bleach, in concentrations available to most households, raises the pH of plants in order to kill them.
Add 1 cup of bleach to a 1 gallon container then fill with water to make a 4 percent bleach solution.
Pour the solution into a spray bottle.
Spray one or two weeds so that all the plant tissue is saturated just before the point of runoff. Then wait 24 hours. If the weeds are not visibly affected, double the concentration of your bleach weed killer then test again (fill your container with 2 cups of bleach then fill with water). Continue the test/doubling cycle until you find the solution that works for the weeds in your yard. Then spray the entire weed population.
Dig up the roots of perennial weeds. Household weed killers do not penetrate to the roots of weeds. Annual weeds can be killed with one spray, but perennial weeds can produce another round or two of foliage from the energy stored in their roots.
Re-spray any weeds that crop up again.