Recipes for homemade weed killers abound on the internet. University of Illinois Extension specialist Michelle Wiesbrook explains why homemade is not always better.
“It's important to keep in mind that anyone can post anything and make it look believable,” Wiesbrook says. “All the author needs is a recipe using easy-to-access ingredients, an adjective like ‘amazing’ or ‘best,’ and a pretty picture to draw attention to it. These little DIY gems spread like wildfire on social media.”
Popular mixes tend to include one or more of these main ingredients: vinegar, boiling water, bleach, baking soda, alcohol, salt, dish soap, and borax. We tend to associate a certain comfort level with these products. After all, they can often be found around the home and some of them are even edible!
Unfortunately, the disadvantages of these home remedies often outweigh the advantages. These products don't contain labels with safety or rate information, and yet they can still be hazardous to your health.
Let’s start with vinegar. Vinegar can be effective for weed control, but only if it is a strong enough grade, which the bottle in your kitchen likely isn't. Vinegar contains acetic acid that in concentrations over 11 percent can cause burns if it gets on your skin and permanent corneal injury if it comes in contact with your eyes. This is why reading and following the label is so important. There are now registered herbicidal vinegar products you can buy that have use and safety information on their label.
What about borax? Although borax may sound like a "natural" weed-control method, it is important to remember that it can still be harmful to children and pets and mixtures should be kept out of their reach.
“Registered pesticides that have been studied extensively come with labels that tell you how to protect yourself and others,” Wiesbrook points out. “The borax box only tells you how to wash your clothes.”
A problem with using borax is that the chemical it contains, boron, does not break down or dissipate like conventional weed killers do, so repeated or excessive applications can result in bare areas where no vegetation can grow. Similarly, salt, which is sometimes used for long-term weed control, destroys the soil structure and is mobile, meaning it can migrate to nearby areas in your garden, resulting in unwanted plant damage.
Some homemade weed-killer ingredients can have a lasting effect on the soil making it so that nothing will grow there for a long time. Depending on the area and what you are trying to accomplish, that may not sound so bad. Yet, conventional herbicides are made to break down or dissipate in a timely fashion. While it is frustrating to see new weeds grow back, it’s reassuring to know the soil is still healthy enough to promote growth.
On the other hand, one other important disadvantage of some homemade weed controls is that they often work only temporarily or only partially affect the top growth. Take boiling water, for example. Pouring it on green leaves would mean certain death, but the roots underground are still protected.
“If your weed is a perennial or if it has a deep taproot, you can bet it will grow back,” Weisbrook says. “Plus, how safe is it to carry big pans of boiling water out the door to your garden? Everything has a risk, and furthermore everything can be toxic or dangerous—even water.”
Some claim that their recipes or methods are more effective or longer lasting than registered herbicides. What about their environmental impact? Are these products mobile in the soil? Will they end up in the groundwater? Have they been tested for this use? Would U.S. EPA approve these weed control methods? If not, would they insist the contaminated soil be removed?
Finally, money savings is often what drives the use of these mixtures. But how much are you really saving? When calculating this, be sure to factor in your personal safety, any potential environmental damage, and the expected length of control. Don’t cut corners when it comes to these important factors—even if the recipe does sound “amazing.”