Bleach in the Garden? Let’s Talk…
We know you want those weeds gone fast. Bleach will damage them, but it also damages paving, harms soil life, and the weeds often grow back anyway. If you want results without the risks, there’s a smarter approach.
Does Bleach Kill Weeds?
Yes, bleach will kill weeds. The sodium hypochlorite in household bleach is toxic to plant tissue and will damage or destroy most vegetation it contacts. However, whether you should use it is another question entirely.
Bleach works as a homemade weed killer, but it wasn’t designed for this purpose and comes with drawbacks that purpose-made weed killers don’t have. It can stain or discolour paving, harm beneficial soil organisms, and may even be illegal to use as a herbicide in some areas.
That said, we understand the appeal. You’ve got a bottle under the sink, the weeds are annoying you, and you want them gone today. So let’s look at what actually happens when you use bleach on weeds, and whether it’s worth the trade-offs.
How Does Bleach Kill Weeds?
Bleach kills plants through chemical burns. When sodium hypochlorite contacts plant tissue, it destroys cell membranes and denatures proteins, essentially dissolving the plant from the outside in. It’s the same mechanism that makes bleach effective as a disinfectant – it’s toxic to living cells.
Unlike systemic weed killers that are absorbed and transported throughout the plant, bleach primarily damages what it directly contacts. This means it works best on small weeds where you can thoroughly coat all the foliage. Larger weeds or those with extensive root systems may survive and regrow.
Bleach also affects soil pH dramatically, making the treated area inhospitable to plant growth for weeks or months. This can be useful if you never want anything growing in that spot, but problematic if you change your mind later.
Our Bleach Test Results
We tested household bleach on weeds growing between paving slabs to see how it compares to other methods. We applied undiluted bleach directly to the weeds on a dry day.
Within three days, the weeds showed significant damage – browning leaves and wilting stems. After a week, most of the visible growth appeared dead.
However, bleach didn’t outperform a proper strong weed killer, and we noticed some discolouration on the paving where the bleach had splashed. For deep-rooted perennials like brambles, ivy, or nettles, bleach simply isn’t strong enough to reach and destroy the root system.
The Risks of Using Bleach
Before reaching for the bleach bottle, consider these potential issues:
Surface damage: Bleach can stain, discolour, or even damage concrete, stone, and block paving. The very surfaces you’re trying to keep weed-free may end up looking worse than they did with the weeds.
Environmental concerns: Bleach doesn’t discriminate. It will harm beneficial insects, soil microorganisms, and any wildlife that comes into contact with treated areas. If it runs off into waterways, it’s toxic to aquatic life. Using bleach as a herbicide may actually be illegal in your area – check with your local authority.
Soil contamination: The high pH left behind by bleach can persist for months, preventing anything from growing in treated areas. If you later decide you want to plant something there, you’ll have a long wait.
Personal safety: Bleach requires proper protective equipment – gloves and eye protection at minimum. Never mix bleach with other chemicals, as this can create toxic gases.
If You Still Want to Use Bleach
We’re not going to tell you what to do in your own garden. If you decide to use bleach despite the drawbacks, here’s how to minimise the risks:
Wear rubber gloves and eye protection. Apply on a calm, dry day – wind can carry bleach spray onto plants you want to keep, and rain will wash it into areas you didn’t intend to treat. Keep children and pets away until the treated area is completely dry.
Use it sparingly and only on hard surfaces like patios, driveways, or block paving where you don’t mind if nothing grows. Never use bleach near lawns, vegetable gardens, flower beds, or water sources.
For best results, pour undiluted bleach directly into paving cracks rather than spraying. This concentrates the effect where you need it and reduces the risk of damaging surrounding surfaces. Check back after a few days to a week – you may need a repeat application for stubborn weeds.
Better Alternatives
If your main concern is avoiding commercial herbicides, there are safer DIY options than bleach. Vinegar provides similar contact-killing action without the environmental toxicity, though it’s no more effective at killing roots. Salt and boiling water are other options worth exploring.
For persistent weeds or larger areas, a long-lasting weed killer designed for paths and paving will give better results with less risk to your surfaces. These products are formulated to kill weeds effectively while being safer to use around the garden than household chemicals never intended for this purpose.
If you’re dealing with tough perennial weeds like bamboo or deep-rooted problems, you really do need a systemic product containing glyphosate that can travel down to the roots. Contact killers like bleach simply won’t kill weeds permanently in these cases.
For a full comparison of DIY methods and their effectiveness, see our guide to homemade weed killers.
Keep the Bleach Under the Sink
Purpose-made weed killers work better, won’t stain your paving, and are actually designed to be safe when used as directed.
I have a bad problem with weeds coming through the cracks of my travertine pavers. If i use a weed whacker to cut the weeds flush to the paver and then spray bleach will that work and keep the weeds down a while for at least 2months due to the fact I am not always at my Florida home I go back and forth about every 6 to 7 weeks.
Should work but check on a small area first, don’t want to damage your pavers
I used concentrated bleach, that is, the one which is used for disinfecting swimming pools („liquid chlorine“, which in fact is sidupium hypochlorite solution) to clean off the black algae and moss from my roof tiles, and it worked amazingly well. That is what professional cleaning services use for that purpose as well. Some of the bleach got onto a small section of my grass, which was full of weeds anyway. Of course it killed off both the grass and the weeds that it came into contact with, but my wife then put fresh grass seed onto that area, and it grew immediately, and is now the part of my lawn with the most grass, and the least amount of weeds..