Will Coffee Grounds Kill Ants: How to Get Rid of Ants Naturally

Coffee grounds are potentially one of the most environmentally-friendly methods of repelling ants. As a plant-based material, there are no harsh chemicals to worry about. The high nitrogen content and acidic profile in coffee grounds may also double as a fertilizer and attract beneficial earthworms which is more than we can say for that can of Raid.

Will coffee grounds kill ants? Coffee grounds, either fresh or recycled will not kill ants unless they are combined with other ingredients like hot water or borax. For example, boiling coffee can be poured into an anthill to effectively eradicate these pests. In this case the hot water is what kills the ants and the coffee may provide a residual effect repelling any survivors.

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Ants are a common pest plaguing homeowners in all areas of the United States. No doubt, they are one of the easiest to attract and most challenging to get rid of. Ants are easily the largest nuisance pest around. 

Common chemical deterrents are effective but pose some unintended health risks for some people and pets. These risks leave many homeowners looking for ways to naturally repel ants and pesky bugs. Among the choices for natural pest control may be coffee grounds. 

Will Coffee Grounds Kill Ants?

Using coffee grounds to kill or repel ants naturally is somewhat of a wives’ tale. While coffee grounds by themselves will not kill ants, they do effectively deter many species. 

If killing the ants is your end goal, you will be better off using a commercial product or a natural approach – boiling coffee poured directly into an ant mound. It is the boiling hot liquid that does the work here. The strong coffee aroma will have more of a residual effect to deter any survivors from staying in the area.

How to Use Coffee Grounds to Manage Ant Infestations

Ants in the garden are not necessarily a problem. In fact, they offer benefits of improving soil structure and eating other insects while generally maintaining a neutral effect on the plants. Sometimes, ants mistakenly build their nests too close to a favored plant, which causes resource problems.

two black ants, will coffee grounds kill ants

Harsh chemicals have no place in the garden – they will likely only kill the plants and be minimally effective at relocating the ant colony. However, coffee grounds are perfect for this use. 

Soaked coffee grounds can create a physical barrier around the plant with a strong odor that deters the ants from returning to this area. Since coffee grounds alone will not kill the ants, this is one of the friendliest ways to manage ant infestations in the garden.

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If you don’t have a plant to protect, say you just want to keep them out of your home, then circling the house with a barrier of coffee grounds is too big of a task. Plus, you will have to replace the grounds often. Sure, it might make for some interesting mulch, but there is a better way. Instead, find the ant mound and place a heap of soaked coffee grounds directly on the mound. 

Why do Coffee Grounds Deter Ants?

Ants get where they are going by following scent trails. Coffee grounds have a strong scent, and they may disrupt this process by covering up the existing scent trail. The particle size also acts as a physical barrier that can serve as a second layer of protection to deter ant activity in an undesired location.

Not all species of ants respond in the same way to coffee grounds. Some species seem to be completely unaffected, while others are only temporarily deterred. The best practice to naturally repel ants with coffee grounds is to create a barrier with used grounds around a plant that you want to protect, or as a way to block entry into the home.

How do Plants Respond to Coffee Grounds?

In addition to potentially deterring ants from your home or favorite plants, as a plant-based material, coffee grounds seem to do a lot more good than harm in the garden and surrounding landscaping. Primarily, coffee grounds and used coffee filters are compatible with compost and fertilizer for gardening.

Close-up of human hands holding a piece of old Coffee Grounds after it’s brewed, will coffee grounds kill ants

Plants that Like Coffee Grounds

Coffee grounds allegedly help increase the soil’s acidity, which is excellent news for plants that thrive in acidic conditions – and not as much for those that don’t. Let’s start by taking a look at the ones that do prefer acidic conditions. The first one is an easy guess, the tomato plant. Although this one is relatively easy to grow without the hassle, some gardeners insist that adding coffee grounds as a fertilizer to tomato plants produces large, juicy fruit.

Next up is rose bushes. If you have ever laid eyes on a thriving rose bush, you know how large they can grow. Some gardeners seem to have a magic touch when it comes to these flowering plants. Rather than magic, they probably just understand a thing or two about soil pH. A healthy rose bush is another place that you can safely use coffee grounds.

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Rose bushes aren’t the only flowering plant that benefits from coffee grounds. Spring bulbs like tulips and daffodils like the acidic pH, as well as rhododendron and blueberries. It turns out the coffee grounds are quite high in nitrogen. This attracts beneficial earthworms, which help aerate the soil. The combined effects of aerated soil with a high nitrogen content and an acidic pH helps these plants thrive.

Plants that do Not Like Coffee Grounds

Not all plants thrive in acidic environments. In fact, coffee grounds used as fertilizer or even as an ant barrier near some plants can do more harm than good. The differences are not that unusual, considering that plants’ species have evolved to thrive in all kinds of different environments, from dry deserts to saturated rainforests.

As a generalization, dry soil loving plants tend not to thrive with the coffee grounds method. Dry soil plants include black-eyed Susan, pothos, lavender, and rosemary. Dry soil plants aside, there is some debate about whether coffee grounds belong in the garden at all. The naysayers range from those who fail to see any benefit from using coffee grounds to those who feel like it is downright harmful. Side note: these are probably the same folks who don’t drink coffee, to begin with, and don’t know what sort of magical elixir it is.

What to Know About Using Coffee Grounds in the Garden

If you are in the party that favors using coffee grounds in the garden, there is another debate to be had. Should you use coffee fresh (dry) coffee grounds or recycle used coffee grounds? It seems that there are some fundamental differences between the two, and it might depend on the application.

Acidity in Coffee Grounds is Water Soluble

One of the key benefits touted by fans of coffee-ground-gardening is its ability to change the soil’s acidity. On the surface, it makes sense; coffee is an acidic drink, and coffee grounds are naturally acidic. Unfortunately, when you brew a cup of joe, the coffee is acidic while the used grounds are basic. If changing soil pH is your goal, you are better off using fresh grounds mixed in with your soil as a fertilizer.

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Coffee has Antibacterial Properties

Another common use for coffee in the gardening community is as a catalyst for composting. But the debate is raging here as well. As a plant-based material, coffee generally does well in compost. One common mistake though, is adding too much coffee to your compost. 

Since coffee is a plant-based material, it is a green addition to your compost, meaning that you need more browns like decaying leaves to balance it out. The dark color of coffee grounds is confusing, causing many people to overdo it with the coffee grounds.

With too much coffee in the compost, two things happen that aren’t that good for your compost pile. The first is that decaying coffee grounds release chemicals that are harmful to earthworms and other beneficial soil inhabitants. The second thing that happens is that coffee has antioxidant properties and can kill off the good bacteria that fuels your compost.

The Takeaway on Ants and Coffee Grounds

Coffee grounds, either fresh or spent, used to naturally repel ants has been something of a wives’ tale. Many master gardeners swear by coffee grounds. Some appreciate the potential to repel ants from overtaking certain plants, and others enjoy it as an addition to fertilizer for juicy fruits and beautiful blooms.

For every person who swears by the power of using coffee grounds is another who is quick to write it off. When it comes to deterring ants, it seems that some species of ants respond better than others. And, some are just more efficient at removing the obstacle from their desired home. Either way, if you have an ant problem and can surround an object like a plant with grounds, it is worth trying. 

Recycling used grounds are the best option for creating a physical and olfactory barrier for repelling ants. But if you are looking to fertilize or compost, fresh grounds are probably going to work better. The key here is quantity. People tend to overdo it on coffee grounds. In contrast, gardening and oversaturating the soil with coffee grounds tend to have the opposite of the desired effect – killing earthworms that aerate the soil and eliminating good bacteria that composts decaying materials.

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