Does Baking Soda Kill Weeds?

Does Baking Soda Kill Weeds?

Partly – but with significant limitations. Baking soda (sodium bicarbonate) is a mild alkaline substance that can damage small, shallow-rooted weed seedlings, particularly those growing in paving cracks. However, it’s too mild to affect established weeds with proper root systems, and it’s strictly a contact treatment that can’t reach underground.

If you’re looking for a relatively safe way to treat tiny weeds in your patio joints, baking soda might help. For anything more substantial, you’ll need a proper weed killing solution.

How Baking Soda Affects Weeds

Understanding what baking soda does explains both its limited uses and its limitations:

Alkaline damage. Baking soda is mildly alkaline (pH around 8.3). When applied to plant tissue, it can disrupt cell function and draw moisture out of leaves. This works best on young, tender growth.

Contact only. Like other DIY weed treatments, baking soda only affects tissue it touches directly. It doesn’t absorb into plants and travel to roots like systemic herbicides do.

Mild action. Compared to salt or vinegar, baking soda is gentler. This is both its advantage (less soil damage) and its limitation (less effective on tough weeds).

When Baking Soda Can Work

To be fair, there are situations where baking soda provides some weed control:

Tiny seedlings in paving. Weed seedlings just emerging between slabs have minimal root systems and tender tissue. A generous application of baking soda can damage or kill these before they establish.

Repeated preventative treatment. Regular baking soda applications to paving joints can help prevent weed establishment. The alkaline environment discourages germination.

Safer than salt. Unlike salt, baking soda doesn’t persist in soil for years. If you’re treating path weeds near borders, baking soda is a lower-risk option than sodium chloride.

When Baking Soda Fails

The problems start with any weed that’s properly established:

Anything with a taproot. Dandelions, docks, thistles – these weeds store energy in deep roots that baking soda can’t reach. Damage the leaves, and they’ll regrow.

Spreading root systems. Weeds like bindweed, ground elder, and couch grass spread via underground runners. Surface treatment is meaningless – the network keeps expanding.

Woody weeds. Brambles, ivy, and similar woody plants have tough stems that resist mild alkaline treatment. Their extensive root systems ensure survival.

Established lawn weeds. Weeds growing in lawns have developed root systems that easily survive baking soda application.

How to Use Baking Soda on Weeds

If you want to try baking soda on small path weeds:

Apply directly. Sprinkle dry baking soda generously onto weeds, focusing on the crown and leaves. A thick layer works better than a light dusting.

Choose dry weather. Apply when rain isn’t forecast for 24-48 hours. Water dilutes and washes away the baking soda before it can work.

Repeat as needed. One application rarely eliminates weeds. Plan to reapply every few weeks during the growing season.

Or make a solution. Dissolve 2-3 tablespoons of baking soda per litre of water and spray onto weeds. This can provide more even coverage.

Common Mistake: Mixing with Vinegar

Many Pinterest and TikTok “recipes” suggest mixing baking soda with vinegar. This is a chemistry mistake:

They neutralise each other. Baking soda is a base, vinegar is an acid. When mixed, they react and neutralise – the impressive fizzing is carbon dioxide being released. What’s left is essentially salty water with minimal weed-killing properties. See our guide to baking soda and vinegar weed killer for the full explanation.

Use one or the other. Vinegar alone or baking soda alone have some effect. Together, they cancel out. Don’t waste both ingredients.

Comparing DIY Methods

How does baking soda compare to other household weed treatments?

Baking soda: Mild, safer for soil, works on tiny seedlings only. Multiple applications needed.

Vinegar: Slightly stronger on foliage, still contact-only. Doesn’t affect roots.

Salt: More effective on small weeds, but damages soil for years. Avoid near borders.

Boiling water: Kills on contact, no chemical residue. Impractical for large areas.

Bleach: Burns foliage effectively but adds chemical hazards without reaching roots.

For established weeds with root systems, none of these work. You need systemic herbicide that travels to roots.

What To Use Instead

For effective weed control beyond tiny paving seedlings:

Path weeds: A glyphosate-based weedkiller kills path weeds root and all, preventing regrowth. One application does what multiple baking soda treatments can’t.

Established garden weeds: Systemic herbicides travel from leaves to roots. A strong weed killer handles the weeds baking soda can’t touch.

Lawn weeds: Selective lawn weedkillers kill weeds without harming grass – something baking soda can’t selectively do.

The Verdict

Baking soda has earned a minor place in the DIY weed control toolkit. It’s safer than salt for your soil, can help with tiny seedlings in paving cracks, and poses minimal environmental risk. But it’s genuinely too mild to affect established weeds with proper root systems.

Use it for path maintenance if you prefer gentle methods. For real weed problems, use real weedkiller.