Organic Herbicides as Alternatives to Chemical Herbicides
In Are We the Pests We’re Getting Rid of?, we discussed the damage that pesticides do to the environment and to human health. Rather than using chemical pesticides, a wide range of safe organic alternatives are available, many of them with specific targets. In this post, we’ve listed some common alternatives to herbicides – that is, substances that are designed to kill weeds and unwanted vegetation -- that are environmentally friendly.
Often, bioherbicides are target-specific. So if a particular bioherbicide doesn’t kill your unwanted weeds or other vegetation, try another bioherbicide. Do not spray with the standard commercial chemical herbicides!
| Corn gluten meal | Broadleaf and grass weed species | Works only if applied prior to germination. Apply in spring to control spring weeds, fall to control fall weeds; may require much more frequent application. Also serves as an organic fertilizer. Available from hardware stores and garden centers. |
| White mustard seed meal | Broadleaf and grass weed species | Found to be more effective than corn gluten meal in a 2017 study. |
| Table salt (sodium chloride) | All vegetation | Mix with water. If used to kill weeds that grow in among plants or grass, use a mixture of 1 part salt to 2 of oil and spray each weed individually. Use a higher concentration (2:1 or 3:1) where weeds are not intermixed with other vegetation. For more information, see Killing Weeds with Salt. |
| Vinegar | Numerous weed species | A 2002 study found that a 5-10% concentration of vinegar mixed with water effectively kills young weeds; higher concentrations kill weeds in all growth stages. There is some evidence that vinegar can be effective against weeds but not surrounding vegetation (corn fields were unharmed by a 20% concentration of vinegar), but more research is necessary. The best approach is to spray each weed individually. Vinegar available in grocery stores has approximately a 5% concentration. Higher concentrations are available from lawn and garden stores. |
| Boiling water | All vegetation | Just pour boiling water on any weeds you’d like to eliminate. Note that you must target the weeds on a weed-by-weed basis; boiling water will destroy all vegetation. |
| Essential oils from red thyme, summer savory, and clove (among others) | Dandelion and other weeds | Essential oils, which are oils extracted from plants, have been shown to be very effective as herbicides. They typically tend to be target-specific, so do further research before selecting one or rely on trial and error to determine if a particular essential oil is effective. Essential oils can be purchased at health food stores and online. |
| Essential oil from cinnamon | Dandelion | A study found essential oil of cinnamon to be the most effective bioherbicide to eliminate dandelions. Another study found it to be the most effective essential oil for weed control when compared with lavender and peppermint oil. |
| D-Limonene(citrus oils from orange, lemon, lime, grapefruit, etc.) | A broad range of weeds, as well as all other vegetation | Citrus oil (and D-Limonene) is a natural degreasing agent that dissolves the waxy coating on plant cell walls, which leads to dehydration and death. It is not target-specific. Citrus oils are the most common ingredients in organic cleaning agents and soaps. They can be used in spray bottles to target weeds. You can purchase D-Limonene at health food stores, garden centers, and online. A 50-55% concentration can be effective against many weeds. |
| Other essential oils | Target-specific weeds | For a list of other essential oils and the specific weed types that they are effective in destroying, see Use of natural products for weed management in 3 high-value crops: An Overview. |
This is by no means a complete list, and as interest in bioherbicides grows, the list of organic herbicides will continue to grow. To find a herbicide that is effective against a particular weed type, just use your favorite search engine to search for "organic herbicide for <name_of_weed>".