In recent years, a number of well-meaning individuals have turned to homemade weedkiller recipes-often shared on social media, as an alternative to commercial herbicides. These typically include concoctions of vinegar, salt, bleach, or washing-up liquid. While they may seem like "natural" or environmentally friendly options, the reality is very different.
What many people do not realise is that in the United Kingdom, using homemade weedkillers is illegal. This is not to be ignored as it is a matter of public safety, environmental protection, and legal compliance.
The law applies not just to commercial products, but to any substance deliberately used to control or kill plants. That includes DIY or "natural" mixtures-regardless of how seemingly harmless their ingredients may be. If you spray a mixture of vinegar and salt to kill ragwort, you are technically applying an unauthorised pesticide, and that is a criminal offence under UK law.
Under Article 28 of Regulation 1107/2009, it is specifically stated:
"A plant protection product shall not be placed on the market or used unless it has been authorised."
This means that unless a product appears on the official HSE list of approved herbicides, you may not legally use it-not even on your own property. Supporting this regulation are the Plant Protection Products Regulations 2011 and the Official Controls (Plant Protection Products) Regulations 2020 (UK Government 2011), which provide enforcement mechanisms and penalties for misuse.
So while many of these homemade mixes might seem benign, their unregulated use poses serious environmental and legal risks.
Many homemade weedkiller recipes include some form of washing up liquid or detergent. These are often used to break down the waxy coating on plant leaves and help other ingredients penetrate more effectively. However, the choice of surfactant-the chemical that makes soap foam and spread-has a major impact on environmental safety.
In the mid-20th century, early detergents were based on branched alkylbenzene sulfonates (commonly called B-ABS). These compounds were effective cleaners but had one critical flaw: they were not biodegradable (Swisher 1987).
These surfactants persisted in the environment for weeks or even months, accumulating in waterways and causing foaming problems in rivers and sewage treatment plants. They were also toxic to aquatic life, with lethal concentrations for fish in the range of 1-10 mg/L (Ying 2006). By the 1960s, their use was phased out in favour of more environmentally friendly alternatives.
Today, most detergents use linear alkylbenzene sulfonates (LAS). These compounds have a straight hydrocarbon chain instead of a branched one, allowing microbes in sewage treatment plants to break them down more easily (Scott & Jones 2000).
Under aerobic (oxygen-rich) conditions-such as those found in most modern wastewater treatment systems-LAS degrades rapidly, with removal efficiencies as high as 97-99% (Temara et al. 2008). The breakdown process begins with oxidation of the alkyl side chain, followed by conversion to smaller, non-toxic fragments. The final products are carbon dioxide, water, and biomass.
Nonetheless, even these modern surfactants can still be toxic to aquatic organisms if released into waterways without treatment. The typical lethal concentration to 50% of fish tested for LAS is around 2-5 mg/L (Chen et al. 2025).
When homemade herbicides containing wsshing up liquid are sprayed outdoors, there is no control over where the residues end up and they may be washed into rivers or soil, or affect non-target organisms like pollinators and amphibians. This is precisely why regulation is necessary.
Whether you're tackling ragwort or any other weed, it's crucial to follow the law and use only approved and tested herbicides. Homemade remedies are not only ineffective in many cases-they are also illegal and potentially harmful to ecosystems you're trying to protect.
References:-