Some of the best organic weed killers include vinegar, salt and boiling water, according to Good Housekeeping. These substances are not chemical, do not contaminate water supplies and are easy to find at home.
To kill weeds with vinegar, spray undiluted vinegar onto the weed's leaves. Gardeners can also make a mixture of one gallon of vinegar and one cup of salt to spray on the leaves. One part salt, eight parts hot water and a squirt of dish soap is another effective spray.
To kill weeds with boiling water, boil a pot of water and pour it over the stems and leaves of the plants. This is a handy way to get rid of large amounts of weeds in driveways and patios. Although boiling water is very environmentally friendly, it can easily kill flowers and vegetable plants, so gardeners should avoid using boiling water near their garden plants.