Does Salt Kill Weeds?

Does Salt Kill Weeds?

Yes, salt can kill weeds – but it’s far from the miracle solution the internet makes it out to be. While table salt will damage plant tissue and can kill small, shallow-rooted weeds, it comes with serious drawbacks that make it a poor choice for most gardening situations.

The Romans allegedly salted the earth at Carthage to prevent anything growing there for generations. That should tell you something about using salt in your garden. It works by dehydrating plants and making soil inhospitable to growth – which sounds great until you realise that includes everything you might want to grow there in future.

We’ve tested salt as a homemade weed killer and while it does have some effect on small weeds, it’s nowhere near as effective as proper weed killers and comes with risks that most gardeners don’t consider.

How Does Salt Kill Weeds?

Salt kills plants through a process called osmotic stress. When you apply salt to a weed, it dissolves in any available moisture and is absorbed by the plant. Inside the plant cells, the high salt concentration draws water out through osmosis, essentially dehydrating the plant from the inside out.

Salt also disrupts the plant’s ability to absorb water and nutrients from the soil. Even if there’s plenty of moisture available, a salt-contaminated plant struggles to take it up. The result is wilting, browning, and eventually death – at least for the parts above ground.

The problem is that salt, like vinegar, primarily affects the visible parts of the plant. Deep root systems of established perennials like brambles, ivy, and nettles often survive and regenerate. You’ll see the top growth die back, feel satisfied, then watch in frustration as fresh shoots emerge a few weeks later.

Our Salt Test Results

We tested ordinary table salt – the cheap 27p stuff from the supermarket – on weeds growing around our test garden. No special “garden salt” needed; any sodium chloride will do the job.

We sprinkled salt generously over several weeds and waited for rain to dissolve it and carry it into the plant tissue. Within 24 hours, there was visible wilting.

After 10 days, the treated weeds looked thoroughly dead. The salt had done its job on the visible growth. However, we noticed that the surrounding soil had a white crusty appearance, and nothing else was growing in those spots either – including plants we wanted to keep.

The bigger issue became apparent over the following weeks. Several of the “dead” weeds began showing fresh growth from their root systems. The salt had killed the top growth but hadn’t penetrated deeply enough to destroy the roots entirely. Compare this to a strong systemic weed killer that travels through the entire plant and kills roots completely.

The Hidden Cost of Salt

Here’s something most articles about salt as a weed killer don’t mention: it actually works out more expensive than commercial weed killers when you factor in coverage and effectiveness.

A 27p container of table salt will treat roughly one square metre of weeds – and you’ll probably need to reapply when they grow back. A proper weed killer costs about the same per square metre but actually kills weeds permanently on the first application. When you factor in repeat treatments, salt ends up costing significantly more for worse results.

Then there’s the soil damage to consider. Salt doesn’t break down or wash away quickly. Heavy applications can render soil infertile for months or even years. If you ever want to plant anything in that area – whether grass seed, flowers, or vegetables – you’ll be waiting a long time.

When Salt Might Be Acceptable

Salt isn’t entirely without uses. On hard surfaces where you never want anything to grow – like block paving joints, driveway cracks, or gravel areas – salt can provide some weed suppression without the soil fertility concerns.

It’s also reasonably effective against very young seedlings that haven’t developed substantial root systems. If you catch weeds within the first week or two of germination, salt might actually finish them off completely.

However, for established weeds, perennial problems, or anywhere near plants you want to keep, salt is a poor choice. The same goes for lawns – salt will kill grass just as readily as weeds, and you can’t use it selectively.

Combining Salt With Other Methods

Some gardeners mix salt with vinegar or boiling water hoping to create a more effective solution. While these combinations can increase the immediate damage to weeds, they share the same fundamental limitation: none of them are systemic.

Adding dish soap to salt water helps it stick to waxy leaves, but this still only affects surface growth. For deep-rooted perennials or tough weeds like bamboo, these DIY mixtures simply won’t reach the extensive underground root networks where the plant stores its energy for regrowth.

If you’re determined to try salt, the most effective method is simply sprinkling it dry directly onto weeds and letting rain dissolve it naturally. Diluting it in water actually reduces its effectiveness.

Better Alternatives to Salt

For weeds on patios and hard surfaces, a long-lasting weed killer will give you months of protection from a single application, without the soil contamination concerns. For garden areas, systemic weed killers like glyphosate travel through the entire plant to kill roots completely.

We know commercial weed killers aren’t everyone’s first choice – the appeal of a “natural” solution is understandable. But salt isn’t really any safer for your garden ecosystem than modern herbicides. It kills beneficial soil organisms, prevents plant growth, and doesn’t break down quickly. At least purpose-made weed killers are designed to target plants specifically and degrade after doing their job.

For more information on DIY approaches and their limitations, see our complete guide to homemade weed killers. We’ve also tested bleach and horticultural vinegar if you want to compare options.