Bleach can effectively control weeds, but that doesn’t necessarily mean you should use it. It can kill nearby plants and damage the soil.
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.”
