Borax is not recommended for weed control by official extension services due to inconsistent results, high soil toxicity risks, and the danger of killing everything in your yard instead of just the weeds.
A handful of borax sprinkled on creeping Charlie sounds like a cheap, gentle solution compared to synthetic herbicides. The reality is far messier. While early 1990s research at Iowa State University showed some promise for controlling ground ivy in lawns, that study was never replicated, and the inconsistency in results leaves significant uncertainty. The margin between what plants need and what poisons them is razor-thin with boron, the active ingredient in borax. Here is what the experts actually say, what the DIY method involves, and — most importantly — what works instead.
Does Borax Actually Kill Weeds?
Borax (sodium borate) contains boron, an essential plant micronutrient that stabilizes cell walls and affects protein integration. In high enough concentrations, boron damages and destroys plants indiscriminately. The theory behind using borax for creeping Charlie is that grass tolerates excess boron better than broadleaf weeds do. But that tolerance gap is narrow and unpredictable. Iowa State University’s Yard and Garden Extension explicitly states the study was never replicated and the results are too inconsistent to recommend this method.
What The Borax DIY Recipe Actually Looks Like
If you still want to try the borax route despite the warnings, here is the method circulating online. These steps come from YouTube videos and gardening blogs, not from the manufacturer — 20 MULE TEAM Borax does not endorse this use.
- Mix for 1,000 square feet: Dissolve 8 to 10 ounces of 20 MULE TEAM Borax in 2.5 gallons of warm water. Warm water dissolves the powder faster and more thoroughly than cold.
- Small patch recipe: For a 25-square-foot patch of creeping Charlie, mix 5 teaspoons of borax in 1 quart of water.
- Safety first: Wear gloves and safety goggles. Borax is toxic to people, children, and pets — the estimated lethal dose for adults is 15–20 grams; less than 5 grams can kill a child or pet.
- Application: Transfer the solution to a handheld or backpack landscaping sprayer and spray evenly. Over-application destroys turf grass and prevents new growth.
Why Experts Say To Skip This Method Entirely
The reasons extension services advise against borax go beyond inconsistent results. Boron does not break down or dissipate like conventional weed killers. It moves slowly through soil and can persist for years, causing permanent damage. Repeated applications result in bare patches where nothing can grow. In states like California, natural groundwater boron from former marine sediments already causes toxicity in tomatoes, citrus, and figs — adding borax makes a bad situation worse. Homemade borax mixes also lack safety labels with rate information, making them hazardous to health and the environment.
According to Iowa State University, the most effective control methods for creeping Charlie are persistent hand-pulling and broadleaf herbicides containing triclopyr and 2,4-D. For readers exploring safer alternatives, our borax product recommendations for gardening cover the best options if you do choose this route — but the safest approach remains avoiding it as a weed killer.
Borax For Weed Control: Key Facts At A Glance
| Factor | Detail | What It Means For You |
|---|---|---|
| Target weed | Creeping Charlie (ground ivy) only | Does not work on dandelions, clover, or most other weeds |
| Active mechanism | Boron toxicity at high concentrations | Kills broadleaf plants faster than grass |
| Soil persistence | Years — boron does not break down | One mistake damages soil for seasons |
| Replicability | 1990s study never confirmed | Your results can vary by soil type |
| Cost | 76 oz box: under $4 | Cheap upfront, expensive in damaged lawn |
| Safety rating | Toxic to humans and pets | No safety labeling on homemade mixes |
| Best alternative | Triclopyr + 2,4-D herbicide or hand-pulling | Proven effective by extension research |
Creeping Charlie Control Methods Compared
| Method | Effectiveness | Soil Safety |
|---|---|---|
| Borax DIY mix | Unpredictable; may kill grass | Damages soil for years |
| Triclopyr + 2,4-D spray | High; proven by research | Breaks down in weeks |
| Hand-pulling | Moderate; needs persistence | No soil impact |
| Corn gluten meal | Low for existing weeds | Safe; prevents germination only |
| Boiling water | Kills everything it touches | Safe but non-selective |
Common Mistakes That Ruin Lawns With Borax
The most frequent error is over-application. Spraying larger areas lightly is ineffective; spraying smaller areas with higher concentrations destroys turf grass and prevents regrowth. Boron does not discriminate — it kills all plants if over-applied, including vegetables and desirable broadleafs. Applying borax in soils that already have high natural boron levels leads to toxic buildup and plant loss. And failing to pre-dissolve borax in warm water causes incomplete mixing and uneven application, which creates patchy dead spots. Repeated applications result in bare areas where no vegetation can grow for years.
The Bottom Line On Borax For Weeds
The safest, most effective path is clear: skip the borax. Persistent hand-pulling or a targeted broadleaf herbicide with triclopyr and 2,4-D delivers reliable results without risking long-term soil damage. If you are growing fruits or vegetables nearby, hand-pulling is the only safe choice. Borax is a cleaning product, not a herbicide — and using it as one is a gamble that costs more than the box price.
Iowa State University’s guide on creeping Charlie control contains the most current advice for homeowners dealing with ground ivy.
FAQs
Will borax kill grass along with weeds?
Yes. While grass tolerates slightly higher boron levels than broadleaf weeds, the margin is narrow. Over-application or uneven spraying kills turf grass and leaves bare patches that take months to recover.
How long does borax stay in the soil?
Boron does not break down like chemical herbicides. It moves slowly through the soil and can persist for years, particularly in clay-heavy soils. Repeated applications cause long-term contamination that prevents any plant growth.
Can I use borax on vegetable garden weeds?
No. Boron at levels that kill weeds also damages or kills vegetables, especially tomatoes, citrus, figs, and melons. Even small amounts can accumulate and ruin your soil for edible plants for multiple seasons.
Is 20 MULE TEAM Borax safe for pets after application?
No. The estimated lethal dose for a child or small pet is less than five grams. Animals that walk through treated areas and later groom their paws can ingest dangerous amounts. Keep pets off treated areas entirely.
Does borax work on poison ivy or poison oak?
No. Borax is only theoretically effective against creeping Charlie (ground ivy). It has no known effect on poison ivy or poison oak. Using it on those plants risks killing surrounding grass while leaving the poison ivy untouched.
References & Sources
- Iowa State University Extension. “Can borax be used to control creeping Charlie in the lawn?” Official extension guidance stating borax is not recommended due to inconsistent research and soil toxicity risks.
- University of Illinois Extension. “Homemade herbicide considerations.” Outlines the dangers of homemade herbicide mixes including lack of safety labeling and long-term soil damage.
- Ask Extension (National Extension System). “Borax for weed control.” Confirms borax does not selectively kill weeds and can destroy all vegetation if over-applied.
- ScienceDirect. “Borax — an overview.” Technical information on boron’s role in plant cell walls and toxicity thresholds.
- 20 MULE TEAM Borax. Official product page. Manufacturer information; borax is labeled as a laundry booster, not a herbicide.