Is Bleach as a Weed Killer a Good or Bad Idea? Experts Weigh In

Every gardener faces the same dilemma: How to remove weeds while expending the least amount of effort and avoiding damage to desirable plants. One possible solution is to kill weeds with bleach, and at first glance, that’s an approach with promise. Bleach is a powerful disinfectant that can kill mold and disinfect pool water, so it should be able to make short work of weeds by poisoning their roots, right?

The related question, however, is whether bleach is safe for the rest of the garden. Not according to turfgrass management expert Ryan Walts, who says: “Using bleach is strongly discouraged. It will likely damage the surrounding soil, harming neighboring plants and making it unsuitable for most plants to grow back in that area for a long time.” Lawn expert Chrissie Handley agrees, and so does gardening enthusiast Harry Lloyd.

In this post, we’ll explain why bleach should not be used to kill weeds on your lawn or in your garden and explore some alternative weed control methods.

Does Bleach Kill Weeds?

“Bleach’s harsh chemical nature makes it quite effective at killing weeds quickly,” says Handley. “It damages their cells and shuts off moisture absorption, which kills the plant.” Common household bleach is a solution of sodium hypochlorite (NaClO), which breaks down in the soil to release salt (sodium chloride or NaCl), water (H₂O) and chlorinated organic compounds. By attaching to organic compounds, chlorine essentially neutralizes them, which is great for pool sanitation but not so good for soil health.

Moreover, salt in the soil affects the ability of roots to absorb moisture. Think about what would happen if you drank a glass of seawater. Rather than quenching your thirst, it would make you more thirsty. That’s pretty much what happens to plants. Unable to absorb moisture from the soil, the roots shrivel, and the plants wither and die.

Does Bleach Kill Weeds Permanently?

This depends on a number of factors:

• Concentration of the bleach solution: In an effort to prevent damage to desirable plants, some gardeners dilute bleach in a spray bottle. But if the concentration is too low, weeds may suffer only temporary damage and grow back.
• Depth of the roots: Some weeds, such as dandelions and thistles, have very deep roots that may not be affected unless you soak the soil with the bleach solution. A surface application won’t cut it for such species.
• Annuals vs. perennials: Annual weeds tend to have shallow roots, which makes them likely to be permanently eliminated by bleach application. Perennials, on the other hand, have hardier roots that grow deeper. They may wither after application but can grow back later in the year or next year.

Handley has this advice for the effective use of bleach for weed control: “You should apply it directly to the weed and re-apply often for the best results, as it makes sure the plant is fully dead and has no possibility of growing back.”

Should I Use Bleach to Kill Weeds on My Lawn?

While bleach does kill weeds, the more important question is whether you should, and the experts I interviewed all agree that the answer is no.

“I understand the temptation, but using bleach on weeds is a very bad idea,” says Lloyd. “Bleach does kill weeds, but it also harms everything else it touches, and although you think you’re directing it just at the root of the weed — it’ll spread to your soil.”

Bleach can kill earthworms, insects and microorganisms vital for soil health. It can also spread to the roots of nearby desirable plants, either causing disease or killing them outright.

“Bleach can leave residue behind in the soil and make the soil pH more alkaline, which can affect the growth of plants in the surrounding area,” says Handley. To amplify this concern, Walts adds that it can make the soil unsuitable for most plants to grow back in that area for a long time.

DIY weed control methods

“Baking soda is a much better DIY alternative,” says Walts. He recommends either applying it directly from the box or mixing it with water. Lloyd adds that you should also consider things like vinegar-based weed sprays, boiling water, or even just pulling them out by hand.

If you’re going to use bleach anyway, here’s Handley’s advice: “Try to use it in a targeted and controlled manner, only applying small amounts to the weed directly. Some people use a spray bottle and dilute the solution to try and combat the strength and just re-apply more often.”

Can I Use Bleach To Kill Weeds in My Driveway?

If weeds grow through the cracks in your driveway, you don’t have to worry about harming nearby plants or the soil under the driveway. That makes bleach an effective control method because not only will it kill the weeds, it will render the soil inhospitable for new ones. If you use this method, make a strong bleach solution — the stronger, the better — and be sure to soak the weeds thoroughly to be sure the bleach gets to the roots.

About the Experts

• Ryan Walts is a training manager and business coach at Lawn Squad, a franchise lawn care business based in Columbia, MD.
• Harry Lloyd is a passionate gardener and waste management expert at HIPPO, a rubbish removal service based in the UK.
• Chrissie Handley is a lawn care specialist and gardening expert providing tailored advice on laying turf, garden maintenance and general gardening tips for Online Turf — a turf, soil and compost company based in Lancashire, UK.

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