Vinegar and Washing Up Liquid Weed Killer

Vinegar and Washing Up Liquid Weed Killer

This is one of the most popular homemade weed killer recipes: white vinegar with a squirt of washing up liquid. The dish soap acts as a surfactant, helping the acidic vinegar spread across and stick to waxy weed leaves. It’s a genuine improvement over plain vinegar – but it still has fundamental limitations.

The Recipe

The basic formula is simple:

Ingredients:

• White vinegar (household 5% acidity, or stronger horticultural vinegar if available)
• Washing up liquid (a few drops per litre)

Method:

• Mix vinegar with a small amount of dish soap in a spray bottle
• Shake gently to combine
• Spray directly onto weed foliage on a dry, sunny day
• Avoid spraying plants you want to keep

How It Works

Vinegar burns plant tissue. The acetic acid in vinegar damages cell membranes on contact, causing leaves to brown and wither. Household vinegar (5% acidity) provides mild burning; horticultural vinegar (10-20%) is more aggressive.

Dish soap improves coverage. Washing up liquid breaks surface tension, helping the vinegar spread into a thin film across waxy leaves rather than beading up and running off.

Better contact = better results. More leaf surface contacting the acid means more tissue damage. The soap also helps the solution stick longer, increasing contact time.

What It Can Do

To be fair, this recipe does work in limited circumstances:

Kills small annual weeds. Tiny seedlings without established root systems can be killed by foliage destruction. If the whole plant is just a few leaves, burning those leaves eliminates the plant.

Burns back young growth. Fresh, tender growth is more vulnerable to acid damage than tough, mature foliage.

Good for path cracks. Small weeds in paving joints, where there’s minimal soil for root development, are reasonable targets.

Immediate visible results. Treated weeds show browning within hours on sunny days, which feels satisfying even if regrowth follows.

What It Can’t Do

The fundamental problem remains:

Can’t reach roots. Vinegar doesn’t translocate – it only affects tissue it directly contacts. Underground roots, rhizomes, and taproots remain completely unaffected.

Established weeds regrow. Perennial weeds like dandelions, bindweed, and ground elder store energy in root systems. Burn the leaves, and they simply produce replacements.

Multiple treatments needed. Even for susceptible weeds, one application rarely suffices. You’ll spray repeatedly throughout the growing season.

Weather dependent. Best results require dry, sunny conditions. Rain washes the solution away; cloudy days reduce effectiveness.

Realistic Expectations

If you try this recipe, expect:

Success on: Annual weed seedlings, very young growth, weeds in paving cracks with minimal root space.

Failure on: Any established perennial weed, anything with a taproot deeper than a few centimetres, woody weeds, spreading root systems.

Ongoing effort: Regular reapplication as new growth emerges and treated weeds regrow from roots.

Comparing to Other Methods

How does vinegar and dish soap compare?

Plain vinegar: Less effective because it runs off waxy leaves. The dish soap genuinely helps.

Boiling water: Similar effectiveness (contact kill only), no chemical residue, but impractical for large areas.

Salt, vinegar, and soap: More aggressive but damages soil. Not recommended near areas you want to plant.

Systemic herbicide: Actually kills roots. One application eliminates the plant entirely. More effective but involves manufactured chemicals.

Tips for Best Results

If you want to try this method:

Use on sunny days. Sunlight intensifies the burning effect. Apply in morning for all-day exposure.

Spray when dry. No rain forecast for 24 hours. Dry leaves absorb better than wet ones.

Target small weeds. Focus on seedlings and young growth where you have a realistic chance of success.

Don’t overspray. This mixture damages any plant it contacts. Avoid lawn, borders, and desirable plants.

Repeat regularly. Plan on multiple applications through the growing season for any ongoing effect.

When to Use Real Weedkiller Instead

For serious weed problems, commercial products deliver results this recipe never will:

Strong weed killer: Professional-grade formulations that actually eliminate tough weeds with established root systems.

Long-lasting weed control: Residual products that prevent regrowth for months – something contact treatments can never achieve.

The Verdict

Vinegar and washing up liquid is a legitimate DIY weed treatment – for very limited purposes. It works better than plain vinegar, can kill small annual weeds, and is useful for path maintenance. But it fundamentally cannot eliminate established weeds with root systems.

Use it for tidying path cracks between proper treatments. Don’t expect it to solve serious weed problems.