Most organic weed killers work on the same principle. Once they come into contact with a plant's tissue, they drastically raise or lower its pH, which kills the plant within hours. This method of weed-killing can easily be replicated by household products with very high or very low pHs. Household bleach has a pH of 12.6. and is not only effective but cheap and easy to obtain. And because it must first be diluted. it's possible to treat even a large area of weeds for less than $1.
Cut the weeds back to ground level, using lopping shears or a lawn mower. Allow them to grow back to at least 3 inches before you spray them with the bleach solution. Herbicides work best on actively growing plant tissue.
Mix a solution of equal parts bleach and equal parts water and fill a hand-held spray bottle with it.
Spray the weeds with the bleach spray. Coat as much of the plant tissue as possible (including the underside of the leaves) and stop just before the point of runoff. While you spray, keep in mind that bleach is a non-selective herbicide. It will kill any plant tissue it comes into contact with.
Re-spray the weeds as necessary. Wait at least two days after your last application before replanting the area.