- Organic weed killers are made out of safe and natural ingredients. They are free of herbicides and chemicals. There are four main types of organic weed killers that are commonly used: acidic, fatty acids, germination inhibitors and salt.
- Acidic weed killers contain acidic ingredients such as lemon, lime or vinegar. The acid concentration in the organic weed killer is usually 15 to 20 percent. An acidic weed killer is sprayed directly on the leaves of the weeds. The acid destroys the protective layer of the leaves that it comes in contact with, causing the leaves to quickly die. The acid can also drip down to the roots, causing the roots of the plants to die. Care must be taken to avoid spraying an acidic weed killer directly on plants that you want to keep, because it will kill any plant that it comes into contact with.
- Fatty acid organic weed killers dissolve the membranes of plant leaves, which causes the leaves to dry up and die. A common ingredient in fatty acid weed killers is coconut fatty acid soap. Like with acidic weed killers, fatty acid weed killers will kill any plant that they touch. Avoid spraying plants that you want to keep.
- The most commonly used natural germination inhibitor is corn gluten meal. Corn gluten meal prevents new plants from germinating but does not harm established plants that already have a root system. Corn gluten meal comes in powder or pellet form. It is spread over an area to prevent new weed growth or to kill newly grown weeds that have yet to develop a strong root system. What is nice about corn gluten meal is that it can be spread over an established lawn or other established plants without harming them. It prevents the growth of only new seedlings.
- Garden-variety rock salt is used as a salt weed killer. Salt dehydrates the leaves of plants, which kills them. If the salt is applied to the soil, it will dehydrate the roots and kill them as well. Care should be taken when applying salt to the soil. The salt remains in the soil and with repeated application will make the soil unusable for plant growth. If too much salt is applied in a garden area, the salt can spread to the surrounding soil and kill plants that the gardener wants to keep. Salt is best used in areas where plant growth is not desired, such as in concrete cracks.
