Baking Soda and Vinegar Weed Killer

The Baking Soda and Vinegar Weed Killer Myth

Search Pinterest or TikTok for homemade weed killer and you’ll find countless recipes combining baking soda and vinegar, often with dish soap added. The dramatic fizzing reaction looks powerful. Surely all those bubbles are attacking weeds?

Unfortunately, basic chemistry says otherwise. This combination is less effective than using either ingredient alone – and neither works well anyway.

The Chemistry Problem

Here’s what actually happens when you mix baking soda and vinegar:

Vinegar is an acid. Acetic acid, specifically. It has a pH around 2.5-3. This acidity can burn plant tissue on contact.

Baking soda is a base. Sodium bicarbonate has a pH around 8.3. It’s mildly alkaline and can stress plant cells.

Mixed together, they neutralise. Acid + base = neutralisation reaction. The impressive fizzing is carbon dioxide gas being released as the chemicals react and cancel each other out.

What’s left? After the fizzing stops, you have a solution of sodium acetate (a salt) and water. The pH is close to neutral. Neither the acidic nor alkaline properties remain – you’ve created something less effective than either ingredient alone.

The Chemical Equation

For those who remember school chemistry:

NaHCO₃ + CH₃COOH → CO₂ + H₂O + CH₃COONa

Baking soda + vinegar → carbon dioxide (the bubbles) + water + sodium acetate (a mild salt)

The acetic acid that could burn leaves? Gone. The alkaline baking soda? Neutralised. You’re left with salty water.

Why the Myth Persists

This recipe keeps circulating because:

The fizzing looks powerful. Dramatic chemical reactions seem like they should do something. But the energy released is creating gas, not killing weeds.

Confirmation bias. If someone sprays this mixture on tiny weed seedlings in hot sun, the seedlings might die anyway (from heat, dehydration, or physical disturbance). They credit the “weed killer.”

Social media rewards engagement. Impressive-looking videos get shared regardless of whether the method actually works. Nobody films the follow-up showing weeds regrowing.

It feels proactive. Mixing up a homemade solution feels like taking action. Even ineffective action feels better than doing nothing.

What Works Better

If you want to try DIY weed control, use ingredients separately rather than neutralising them:

Vinegar alone: Can burn leaves of small, young weeds. Still contact-only and can’t reach roots, but at least the acid remains active.

Baking soda alone: May affect tiny seedlings in paving cracks. Mild and slow, but the alkaline properties aren’t cancelled out.

Boiling water: Kills on contact through heat. No chemical residue. Works on small path weeds.

None of these affect established weeds with root systems, but at least they retain their active properties.

For Actual Weed Control

If you want weeds gone rather than temporarily stressed:

Systemic herbicide. Glyphosate-based weedkillers absorb through leaves and travel to roots. One application kills the entire plant, including underground parts that DIY methods can’t reach.

Strong weed killer: Formulated for tough weeds with deep roots. Does what kitchen chemistry can’t.

Long-lasting weed control: For paths and drives, residual weedkillers prevent regrowth for months – something fizzy water will never achieve.

Physical removal: For small areas, digging out roots completely works. Labour-intensive but effective.

The Dish Soap Addition

Many recipes add washing up liquid to the baking soda and vinegar mixture. This is meant to help the solution stick to waxy leaves. But:

You’re helping salty water stick to leaves. The neutralised mixture has minimal weed-killing properties. Helping it stick better doesn’t make it work.

Surfactants help active ingredients. Dish soap can help vinegar stick to leaves more effectively – but only if you haven’t already neutralised the vinegar with baking soda.

Testing the Myth

If you’re sceptical, try this experiment:

Test 1: Spray weeds with plain vinegar.

Test 2: Spray weeds with baking soda and vinegar mixture (after the fizzing stops).

Test 3: Spray weeds with plain water.

You’ll likely find Test 1 causes some leaf browning, while Tests 2 and 3 produce similar minimal results. The neutralised mixture performs barely better than water.

This ineffective approach won’t help with serious weed problems like bindweed or patio weeds – you’ll need proper herbicide for those.

The Verdict

Mixing baking soda and vinegar is satisfying chemistry theatre but terrible weed control. The impressive fizzing is your active ingredients cancelling each other out, leaving salty water behind. You’d get better results using either ingredient alone – and better results still using actual weedkiller.

Save your baking soda for baking, your vinegar for cooking, and use proper products for weed control.