I have used undiluted bleach to zap small nuisance weeds in the cracks of my sidewalk and along the wooden fences of my house since forever. The repeated dose of a strong hypochlorite bleach like Clorox can even nuke noxious species like dandelions. So in short, yes, you can use bleach as a weed killer for isolated weeds that creep up in the driveways, patios, and fences.
But don’t just jump right into a conclusion and start dousing the weeds with gallons of bleach, read till the end to save yourself some nasty troubles down the road.
So How Exactly Does Bleach Kill Weeds?
Concentrated bleach is a very strong chemical. As soon as it gets absorbed by the soil, the pH level of the soil shoots up. This consequently kills the microorganisms that help to transfer the essential nutrients to the plant’s root system. The plants die soon after their source of nutrients is cut off.
You can kill grassy weeds by spraying the bleach directly onto the leaf blades instead of the soil. Bleach disrupts the molecular conformation of the leaves, causing them to slowly turn yellow or white, curl up and/or wither. This leads to the denaturation of protein cells by free oxygen, causing the plants to decompose. To summarize, the weeds are going to die a horrible death.
While killing weed with bleach is definitely much simpler and cheaper than using a regular herbicide, it’s a dangerous chemical that can kill (or cause great harm to) anything living organism that comes in its way. This includes plants, benevolent insects, animals as well as humans.
With that being said, it is safe to use bleach as long you’re using it for spot treating areas where you don’t want to grow any vegetation anytime soon. Bleach tends to seep into the soil and may emit harmful gas, so you would also want to make sure the treated area is not a wildlife habitat.
For the same reason, don’t let your pets hover around the freshly treated area for a couple of days.
For your convenience, let me quickly go over the dos and don’ts of using bleach as a weed killer:
Using Bleach as a Herbicide- The Dos:
- Wear waterproof gloves and eye protection gear while applying bleach.
- Apply the bleach on the hottest days when the weeds are actively growing for fast and effective results.
- 1 cup of undiluted bleach will be enough for most cases. If you are targeting a huge area full of clay, bump it up to 2 cups.
- Wait for 2-3 days for the bleach to take effect. Once the unwanted plants turn dry, discolored, or brown, pull them out.
- Use about a gallon of water for every 6×6 square inch area for flushing the soil after 3 days if you absolutely have to use bleach near plants or grass.
- Choose a rain and wind-free day to prevent the spray from going in directions you don’t want it to.
And now, the Don’ts:
- Refrain from spritzing bleach on the target area near a water body. The solution could seep into the water and contaminate it. Bleach is also extremely harmful for underwater wildlife.
- Bleach can heavily affect the soil integrity. Don’t use anywhere near plants you don’t want to kill. I should also remind you that you won’t be able to grow plants in the treated area for several months. So I’d strongly advise keeping its use limited to cracks into the sideways, patios, and other foundations around your house.
- Don’t let people with serious medical conditions, children, and pets around the treated area until the bleach is completely dry.
- Don’t use too much in one go. Test with a small amount first to see how it goes.
- Strictly avoid spraying bleach anywhere near edible crops.
- Don’t mix bleach with anything else, especially vinegar. Here’s why:
Why You Should Never Mix Bleach and Vinegar to Kill Weeds
Both bleach and vinegar are quite effective at eliminating small weeds. Then why not mix both and kill those pesky weeds even faster? Right? Wrong.
Most off-the-shelf bleach brands use 10-15% of concentrated sodium hypochlorite which is highly alkaline. It is so corrosive that it can torch any plant that comes in contact with it. On the other hand, vinegar is basically acetic acid mixed with water.
You don’t have to Madame Curie to know that acid and alkaline cancel each other out. So if you mix bleach with vinegar, they will neutralize each other. But that won’t be your biggest problem, trust me.
Acid and bleach will produce chlorine gas which is so poisonous that it was weaponized during World War I to kill soldiers. I rest my case here.
In fact, you shouldn’t mix bleach with any other chemical, not even that seemingly harmless dish soap or peroxide-based cleaner sitting on the shelf, for the same reason as above. Skip the ammonia too as it could release chloramine gas that causes severe irritation in the respiratory tract, nose, and eyes. I learned it the hard way.
And as for mixing it with cleaners containing alcohol, here’s something not-so-funny you should know.
When rubbing alcohol reacts with bleach, it produces chloroform along with hydrochloric acid. Unless you want to faint on the spot and feel dizzy, and nauseous all day, don’t do that.
Basically, don’t mix bleach with any other chemical for killing weeds. But since we are on the topic of mixing stuff with bleach, I should tell you that it’s completely safe to mix baking soda with bleach for making homemade cleaning solutions. However, bleach+baking soda won’t really help kill weeds faster.
I would rather you follow the tried and tested method which is as follows:
How to Kill Weed with Baking Soda in 4 Steps:
- Mix equal parts of bleach and water, for example 2 cups of chlorine with 2 cups of cold water.
- Pour the solution in a spray bottle.
- Spray it directly onto the plants you want to nuke and wait for 2-3 days.
- Once you begin to notice the signs of plant injury, pull out the dead weeds.
You can store the leftover mixture in a plastic-wrapped bucket or closed container and use it for up to 24 hours. After that, the solution will begin to lose its strength.
Will bleach kill weeds? Sure it will. But it will also kill all the microorganisms, including the beneficial ones beneath the soil along with weeds. So my suggestion will be to use bleach only in isolated areas, away from the plants you don’t want to kill.
Also, as I have mentioned multiple times in the article, make sure the solution doesn’t come in contact with nearby water bodies or wildlife habitat as this sterilizer can be fatal for them.
As long as you use it wisely and in small amounts, bleach can be a fantastic cure for invasive weeds that grow in the tiniest cracks and crevices in the walkways, driveways, pavements, patios, and stepping stones.