Does Diesel Fuel Kill Lawn Weeds? The Science Behind It

Killing weeds is a great American pastime and something everyone has an opinion about, and most, a nifty trick or two. Older people will have tricks and techniques that, while once upon a time were common practice, may not be such a good idea anymore.

When it comes to which herbicides to use in our yards, it can be hard to choose, especially if there’s a limited budget for grass care.

Products for gardens can be expensive, and a shortcut that is sometimes taken involves concocting a homemade herbicide from other toxic substances and household supplies. White vinegar is a common ingredient and so too is diesel fuel. But how effective is diesel as a weed killer, and should people use it in their gardens? Let’s find out. 

Will Diesel Destroy Lawn Weeds?

Diesel is toxic and will kill weeds but only temporarily, and depending on the aggressive growth of the weeds may not do more than wilt some foliage. A single application will have little effect on anything other than extremely young sprouts, and any weed with an established root system will be better off getting hit with commercial weed killers for faster results. Grassy weeds are exceptionally susceptible to diesel’s toxic substances. 

While it is not an effective weed killer, it will get the job done if no other options are available. A more effective method is to add a little diesel to a spray bottle with another weed killer like glyphosate and spray that on stubborn weeds.

Broadleaf weeds can be quickly dispatched with this method, but it is not even close to a permanent solution and can eventually spread toxins through the soil and kill your desirable plants. 

Does Diesel Harm Grass?

Yes, diesel is toxic to all plant material and will kill plant leaves as well as leach into soil and poison the roots of neighboring plants. The application is far better received in a rock garden with unwanted plants as opposed to a lawn with all types of weeds growing throughout, but even in this situation, groundwater and runoff are still environmental concerns.

Grass that has diesel spilled or sprayed on it will die within 2 days, and subsequent grass will be unable to grow until the spill is cleaned up, and the hydrocarbons have fully broken down, typically several years. 

Using Diesel for gardening is akin to salt and will kill not just the growing plant but also your garden’s ability to produce new plants or soil life. Extreme treatment is needed to replenish areas of land that have been exposed to diesel, and any evidence of a spill on land renders it unable to ever be certified organic for commercial purposes.

It is better to find a more natural product like vinegar or hot water to put in your plastic spray bottle and forego the diesel altogether. 

Lawn Uses for Diesel

The use of diesel for lawn and home tasks is a blatant safety hazard and illegal. In rare cases, we may need to deal with a problem with speed, and if diesel is all that is on hand, it may be acceptable to use a tiny bit. If this happens, safety precautions must be practiced to prevent injury to yourself, nature, or accidentally poisoning drinking water or an irrigation water supply. 

Use	Application	Effect
Weed control	Fill a spray bottle with water and a small amount of diesel, and then spray carefully on pesky weeds	Kills grassy weeds in 48 hrs but will damage soil life and surrounding vegetation, not just unwanted weeds
Cleaning Spilled Paint	Apply diesel, a cloth, and scrub to help dissolve the bonds of the paint, and then hit with a water source to finish the job	Removes paint easier than a water, soap, and scrubbing practice but be careful of diesel runoff in grass and waterways and always have a containment protocol for spilled diesel
Pest Deterrent	Apply diesel onto a rag and hang it in areas where pests enter searching for food or shelter	Deer, rodents, and other wondering pests will turn away at the scent of diesel and leave your lawn alone
Pest Killer	Spray at insect or wasp nests to kill harmful bugs fast	Can poison and kill insects deep in nests and hard-to-reach areas but will harm all life forms in the process
Accelerant	Place diesel in fire safe area and ignite	A reliable combustible that should be used under caution and only with experience or as a last resort.

What is the Best Way to Use Diesel Fuel as a Weed Killer?

If you must use diesel to kill weeds, even though there are countless reasons not to and even more effective and safe alternatives available, then you must do it safely, or you risk doing serious damage and potentially face fines. So before you run to the gas station to get some diesel for your homemade weed killer you want to hit that poison ivy with, review the safest process to achieve your goals with this inferior method of weed killer. 

Check Weather

The right weather is paramount for your success. You want a hot, dry day with low little wind and no chance of rain in the forecast. If it begins to rain too soon after you spray bushy weeds, the toxicity won’t set, and the plants will survive. Even worse, you open up all surrounding vegetation to exposure to the diesel-filled runoff killing much more than your target weed.

Likewise, if it is windy, you will not be able to only hit grass weeds which may damage desirable landscaping plants around your lawn. 

Gather What You Need

First, you will want to grab your gas can full of diesel fuel that you had on hand for this task. If you need to go get the fuel, you should pick up a better alternative and not continue with the steps below. However, if all you have available is fuel for weed removal, grab the rest of your supplies as well.

Get a clean funnel and a rag to help prevent spills, and find the spray bottle you want to use for the task. Also, grab a bucket of sand in case any fuel spills you can contain it and clean it up quickly before contaminating any healthy plants in the area. 

PPE  is needed, including chemical-resistant gloves and not cloth which will absorb the liquid and cause intense skin irritation. Safety glasses with a side cover to prevent fumes and spray particles from blowing into your eyes are also advised. Since you will want to work with diesel on days with low wind, you will have many fumes lingering where you are; a mask with a respirator can help protect you from dizziness and other consequences of inhaling fuel.

Make sure to toss the protective gear and change your clothes when you are done spraying. 

Mix Your Spray 

Place the rag over your hand and grip the top of the funnel while you slowly pour the diesel into the spray bottle. Fill it a little with diesel and the rest of the way with water to avoid too high of a concentration for the prayer to deal with. 

Apply Weed Killer

Hardy plants may need several applications, but the growth of weeds can be halted by just one spray. Unlike systemic herbicides, you will need to keep applying diesel to see any lasting results. Kneel as close as you can to the root zone of the target plant and spray precisely. Only apply enough to saturate the soil immediately around the weed, or you will prevent healthy plant growth for years. 

Clean Equipment

When you are done spraying, clean everything with hot water; make sure to take all parts off and clean each one, as diesel can destroy a sprayer if left inside too long. It is important not to use that sprayer for other organic tasks as it will be impossible to completely remove all traces of the fuel, and any subsequent sprays will release some contaminants. 

Can Diesel Fuel Legally Be Used on Lawns?

While diesel does work as a toxic weed killer, it is also considered an environmental hazard in the US and most countries around the world. The effects on soil life and the ability of the ground to produce life are profound, so it is illegal to dump diesel on the ground. Any spills need to be cleaned up with sand or other products designed to pick up the toxins.  

Along with human and animal injury using diesel as an herbicide represents environmental hazards like contaminated water supply and reduced drinking water, as well as being deadly to livestock and wildlife that rely on watersheds to survive. It creates an additional fire hazard for homes and years, which is especially ill-advised in the age of increased wildfires.

Since diesel is an indiscriminate plant killer, it will eliminate all life wherever it falls.

What are the Main Risks of Using Diesel Fuel as a Weed Killer? 

While it is now common knowledge that diesel is toxic and dangerous to soil microbes and worms, it also destroys healthy roots and mycelium as it is taken into the soil and will lead to barren earth if not remedied. Diesel, as an herbicide, will not prevent weed seeds from germinating once the diesel has been absorbed into the soil, making it far less effective than other solutions. 

Human and pet health risks are real, as pets and kids may play near plants that have been sprayed, and even improper application can result in severe injury. A breeze of wind can lead diesel to kill ornamental plants and your turf. It is not good for the environment and can negatively impact your lawn’s ability to heal and grow naturally in the future.

In some cases, diesel can be mixed with other weed killers to help improve their effectiveness but is not a great option for regular weed-killing practices as, eventually, your lawn will succumb to its pervasive toxic effects. While diesel does kill weeds, it is best to use a safer alternative 100% of the time.