Can You Use Coffee as a Repellent?

Maybe you’re a coffee addict looking to make use of your used grounds. Perhaps you’re a keen gardener desperate to find a more environmentally way to keep slugs and pests away from your rose bushes. Either way, coffee makes an incredibly effective gardening tool. While we might love the smell of a cup of java in the morning, we’re about the only species that does. Waft a freshly brewed cup of espresso under the nose of most creatures, and they’ll be slinking away with their tails between their legs before you know it. Best of all, it’s entirely natural, meaning there’s no need to worry about any dangerous chemicals leaching into your soil and contaminating your vegetable patch. If you’re ever found yourself wondering if you can use coffee as a repellent, here’s what you need to know.

Can You Use Coffee as a Repellent?

Over the past few years, we’ve got used to new hacks popping up on an almost daily basis giving new and ingenious ways of using common household products and kitchen staples. Some don’t work, some are brilliant, and others are too bizarre to even try. So, where does using coffee as a repellent fit into the spectrum? If the anecdotal evidence is anything to go by, it’s looking good. And it’s not just the personal opinions of people who’ve tried it that are convincing – the science seems to be pretty compelling too. According to those in the know, coffee has evolved to be a natural pest repellent. It all comes down to caffeine. Clever plants like coffee, cacao, and tea figured out somewhere along the evolutionary line that pests really don’t like the stuff, so evolved to produce as much of it as possible to protect themselves from being eaten. Obviously, they hadn’t factored humans into all this, which is fortunate for us, but less so far for them. As the only species that considers a highly caffeinated state to be the only way to get through the day, most of us will happily slurp our way through cup after cup of caffeinated goodness to keep the buzz going. Snails, slugs, and other pests don’t necessarily consider feeling sluggish to be a bad thing. Neither do they much like the effect it has on their systems, with the result that they’ll go out of their way to avoid it. As well as repelling slugs and snails, it also seems that coffee can help repel larger critters like cats, rabbits, and deer, making it the perfect, environmentally friendly solution to marauding wildlife.

Do All Kinds of Coffee Work as a Repellent?

In an ideal world, we’d be able to scatter any old type of coffee we like over the garden and kiss goodbye to pesky pests for good. But if the last two years have taught us anything, it’s that this isn’t an ideal word – if you want to get serious about using coffee as a repellent, you’re going to have to get serious about the type of coffee you use. As it’s the caffeine content of coffee that seems to make pests take a running jump, using decaffeinated coffee is obviously not going to achieve the desired result. According to coffeeaffection.com, solutions with 1-2% caffeine kill slugs and snails within two days, and concentrations down to 0.01% caffeine can function as repellents. Coffee beans typically range from 0.8 to 2.8% caffeine, instant coffee comes in at around 0.05% caffeine, and regular brewed coffee is usually the most caffeinated of all. Although used grounds still have some caffeine left in them, it’s at much lower levels than unused coffee, so stick with the fresh kind if you’re dealing with a serious pest problem. There’s also some suggestion that coffee (as in the already brewed variety) is more effective than coffee grounds, potentially because of how much better liquid soaks into the ground. However, both are effective, so don’t feel obliged to brew up a fresh liter of coffee if scattering the grounds is easier for you.

Will Coffee Harm Plants?

As gardenandpatiohomeguide.com points out, coffee is slightly acidic, so isn’t suitable for all plants. Marigolds, daffodils, roses, azaleas, rhododendrons, hydrangeas, lilies, hollies, and lily of the valley all relish acidic soil, as do blueberries, carrots, radishes, and cabbage, so feel free to use coffee around them with impunity. Tomatoes, clovers, alfalfa, geranium, asparagus fern, Chinese mustard, and Italian ryegrass, on the other, won’t appreciate having their roots doused in an acid bath – if you still want to use eco-friendly alternatives to chemical repellents for these kinds of plants, opt for solutions like wheat bran or diatomaceous earth instead.

How to Use Coffee as a Repellent

The method for using coffee as a repellent is straightforward. Depending on whether you choose to use liquid coffee or grounds, here’s what to do: For Coffee Grounds: Simply sprinkle the coffee grounds around the plants. Avoid using large, wet clumps of used coffee grounds as this can attract mold. As coffee has numerous nutrients such as nitrogen, phosphorus, and potassium that can be beneficial for plants, some gardeners like to mix the grounds directly into the soil during planting or re-composting. For Liquid Coffee: Brew a fresh batch of coffee then pour it directly over the soil surrounding the plants you want to protect.

How to Use Coffee to Repel Mosquitoes

So, we know coffee can act as an effective repellent on slugs and snails. But what if we’re keener to protect ourselves from bites than our plants? Can coffee help repel annoying mosquitos too? According to Hunker, it can indeed. It turns out that mosquitoes are just as turned off by the smell of coffee as other garden pests, especially when it involves a bit of smoke. To keep mosquitos from turning your garden into a battleground, here’s what you should do:

Step 1

Add a layer of used coffee grounds to an aluminum foil pie plate and leave to dry.

Step 2

Clear the outside area of kids, pets, and other liabilities before placing the foil plate on a flat, level surface.

Step 3

Add a couple of drops of lighter fluid to the coffee grounds, being careful not to saturate them. Use a candle lighter or long match to light the grounds then wait for them to start smoking.

Step 4

Put out the fire by covering it with a damp towel. Remove the towel and leave the grounds to continue smoldering. Your garden should stay mosquito-free for as long as they keep smoking.