Horticulture Magazine

Can (And Should You) Use Bleach To Kill Weeds?

yellow dandelions in a field

There’s nothing quite as frustrating as weeds.

Whatever you do, however much back-breaking manual labour you put in, their persistent green selves will always find a way back into your garden.

It’s an ongoing war of attrition where the closest you’ll ever get to victory is holding slightly more of them at bay for slightly longer.

As a gardener, it’s like you know this pain fairly well.

Finding The Right Solution

It’s also fairly likely that you’ve considered whether the weapons in your anti-weed arsenal are really strong enough to do the trick.

You’ve covered beds for the winter before growing season to kill off as many as possible.

You’ve forked the soil to remove the most persistent contenders.

hand holding various weeds that have been pulled from the garden
How do you get rid of the confounded things?!

Maybe you’ve even picked out a few by hand: adding the sweat from your brow to the toolkit.

Perhaps you’ve also considered the nuclear option.

Can you use bleach to kill weeds?

adult woman bending to pick weeds from a garden border

If you’re at the end of your gardening tether, you may be looking for something a little more extreme than the techniques you’ve employed so far.

And while you can use bleach to kill weeds, as organic gardeners we strongly advise that you shouldn’t.

In the following sections, we’ll explain briefly why bleach does make a good weed killer, but our overall stance is that you should probably try something else instead.

Bleach causes damage to the soil that can take a long time to correct itself, and there are safer alternatives available.

Bleach does kill weeds: Here’s how

In the same way that bleach is harmful to humans and pretty much every living creature we share the planet with, it’s also harmful to plants. [source]

When bleach soaks into the soil, it makes its way down and kills the plant from the roots upward.

Here’s the kicker, though. Because the pH level of bleach is so high, it makes the soil very alkaline.

As most plants have very specific pH ranges at which they can grow, bleached soil isn’t conducive to plant life or growth, as the high alkaline levels prohibit plants from absorbing the nutrients they need to thrive. [source]

And as a gardener, this is probably reason enough in itself not to slather your garden with the stuff!

close up of a bottle of bleach

Also, a by-product of bleach breaking down is salt, which isn’t a good addition to soil. [source]

There’s a reason why armies salted the earth behind them when they conquered a city: salt attacks plants via osmosis, sucking the moisture from them and slowly killing them. [source]

So, while bleach will be effective against common weeds, the collateral damage really isn’t worth the risk.

And while it works on small weeds, it’s unlikely to make a dent on bigger weeds with dense root systems.

When you consider this fact, it makes bleach an even less viable option for evacuating pesky weeds from your outdoor space.

What about bleach for patios and places with no soil?

weeds sticking out from the crevices of a garden patio

Maybe you’re wondering about using bleach to remove weeds from the cracks between paving stones on your patio, or somewhere else in your garden that doesn’t have soil.

In this instance, we’d still recommend using a product that’s designed specifically for this purpose.

Although you’re not applying bleach directly to the soil, it’s not hard to see how it could make its way there eventually.

When it rains, for instance. Or even as the residue trickles along channels in the slabs.

a sharp, thin tool being used to remove weeds from the cracks of pavement

There are more environmentally-friendly alternatives to consider:

  • Sprinkle baking soda over your patio, sweep it into the cracks with a broom, then add water
  • Use your hands! It’s not fun or particularly glamorous, but it’s an effective way to get rid of them
  • Use special tools designed for narrow spaces. If you can’t fit your fingers into thin crevices between stones, use a tool made for the job
  • Use boiling water. While this method definitely can (and will) kill any other plants and creepy crawlies it comes into contact with, it at least won’t cause lingering damage to the soil

As you can see, there are plenty of viable options to consider before thinking about bleach.

Bleach in your garden: Horror stories

Read around garden forums and you’ll find all sorts of stories about reckless neighbours washing their driveways with generous helpings of bleach, only to end up killing off the carefully tended flowerbeds of nearby homes.

If you’ve been investing time and effort into your garden for many years, there’s nothing quite as soul-destroying as having your work destroyed by such an easily avoidable outcome.

There are also stories of spouses enthusiastically cleaning their garden furniture, only for their partner to find all the nearby flowers dead the next time they head outside to water them.

Whichever side of these potential situations you’re on, hopefully you can see why using bleach in your garden isn’t the best idea.

It’s more than likely that you’ll kill at least something you didn’t intend to, whether it’s your own plants, your neighbour’s plants, or your partner’s respect for you.

“There better not be any bleach in that bucket, Ian!”

Killing weeds with bleach: The verdict

In this article, we’ve tried our best to outline the information around using bleach to kill weeds in your garden.

Our goal has been to show that while you can use bleach in your garden, you probably shouldn’t.

Better alternatives are available, and the amount of damage you risk causing to other plants, creatures, and ecosystems just aren’t worth it. [source]

In short: if you’re looking for effective ways to kill weeds in your garden, there are plenty of steps you can take before needing to consider bleach warfare.

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