As the gardening season gets underway, lots of homemade weed-killer ‘recipes’ crop up on social media, usually containing some combination of vinegar, Epsom salts and Dawn dishwashing soap. These are often accompanied by a comment such as ‘no need for pesticides’. 

 It may feel good to use familiar household items to control pests in your garden, but it’s important to understand the science behind such mixes—and the potential risks. These may be do-it-yourself recipes, but they definitely are not natural. These mixtures are pesticides. They are intended to kill a pest, in this case weeds. 

Vinegar

Vinegar is an acid. At the right concentration, it damages by burning any part of a plant it comes in contact with. If the plant is in the ground, it does NOT get the root; many plants will grow back. It is non-selective, meaning it will damage any plant it touches, including desired ones.  

Household vinegar is 5% acetic acid; to be effective on anything other than tiny seedlings the concentration needs to be at least 10%. Horticultural-grade vinegar is 20% and can carry a ‘Danger - caustic’ signal word, which is stronger than many other herbicides on the market. 

Salt

Salts work by desiccating plants—again, all parts of the plant it touches. Since most homemade recipes need repeated application to be effective, the salts will build up. However, increased salts concentration in the soil can harm desired plants nearby. Epsom salts are touted because they contain magnesium instead of sodium, but too much magnesium will interfere with phosphorus uptake. 

Detergents/Soaps

Dawn detergent is not a naturally occurring substance. It, like any soap, is used as a spreading agent, helping the other materials stay on the plant longer. Like many detergents, it contains methylisothiazolinone, which has acute aquatic toxicity and 1,4-dioxane, which is a known groundwater contaminant with carcinogenic properties.  

An additional issue with home recipes is the variability of the mix. Many don’t even have specific measurements. Also, because home remedies are often perceived as ‘safer’, a person may choose to increase the concentrations, changing the potential environmental risk. This safer perception some have of homemade pesticides is not true though.  

When using homemade or other pesticides, it’s important to follow proper safety precautions to protect yourself, others, and the environment. Always wear personal protective equipment (PPE), including gloves, long sleeves, eye protection, and a mask to avoid skin contact, inhalation, or accidental splashes.  

Work in a well-ventilated area or outdoors, and avoid applying pesticides on windy days to prevent drift. Keep children, pets, and pollinators away from treated areas until the solution has dried.  

Store any leftover mixture safely, clearly labeled, and out of reach of children and animals. Remember, even natural or homemade solutions can be harmful if not handled properly. 

Many of these recipes do reduce or suppress some weeds and unwanted vegetation. But they also have collateral impacts, some of which may be significant. These include making pest problems worse and contaminating groundwater and soil, among other issues.  

Garden center shelves have changed in the last several years. There are now many naturally derived pesticides on the market, that have been tested for effectiveness, are labelled as to their environmental impact, and deliver consistent outcome/results every time. They generally are safer to use and pose less environmental risk than many of the older synthetic materials— the same goal of homemade mixes.  

The Organic Materials Review Institute (OMRI) is a nonprofit organization that provides an independent review of products, such as fertilizers and pest controls that are intended for use in organic production. Look for products that are OMRI certified. 

Resources

Michigan State University Extension. (2016, June 28). Are homemade pesticides legal? https://www.canr.msu.edu/news/are_homemade_pesticides_legal 

University of California Agriculture and Natural Resources. (2021, September 15). UC IPM statement: Homemade pesticides. https://ucanr.edu/blog/coordinator-news/article/uc-ipm-statement-homemade-pesticides 

University of Connecticut Integrated Pest Management. (n.d.). Pesticide safety and use. UConn Extension. https://ipm.cahnr.uconn.edu/pesticide/ 

University of Florida Institute of Food and Agricultural Sciences Extension. (2023, June 27). Pesticide use and safety. https://edis.ifas.ufl.edu/publication/PI288 

Virginia Cooperative Extension. (2022, April 1). Using home remedies to control pests: Are they safe and effective? https://www.pubs.ext.vt.edu/ENTO/ento-570/ento-570.html 

The information in this document is for educational purposes only.  The recommendations contained are based on the best available knowledge at the time of publication.  Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended.  UConn Extension does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.  The University of Connecticut, UConn Extension, College of Agriculture, Health and Natural Resources is an equal opportunity program provider and employer.