People leave used coffee grounds on their porches primarily as a natural, DIY method to repel pests like mosquitoes, ants, slugs, and snails. The strong aroma and texture of the grounds are believed to deter these pests from entering homes or attacking nearby plants.
Instead of throwing spent coffee grounds in the trash, some homeowners leave piles or lines of coffee grounds around their gardens and homes to keep flies, mosquitoes, and other pests away. Coffee grounds are also often used to deter slugs and snails, reduce weeds without chemicals, and even repel neighborhood strays.
Plant Fertilizer
Besides deterring pests, coffee grounds are actually great to add to your garden as a natural fertilizer, specifically for acid-loving plants like azaleas, rhododendrons, and blueberries, says Toner.
Coffee grounds offer a safe method of keeping pests away. They repel ants, mosquitoes, wasps and bees. Additionally, they will keep slugs and snails at bay however a better method is a coffee solution. Slugs tend to turn tail and run when they encounter a caffeinated soil.
Coffee grounds can help repel not only mosquitos but also other annoying insects like wasps and bees. Why are coffee grounds effective? Most bugs have a very strong sense of smell. Coffee grounds have a strong smell but it's even stronger when they are burned.
Mosquitoes hate strong, pungent, or citrusy smells that disrupt their ability to find hosts, with popular repellents including citronella, lemon eucalyptus, lavender, peppermint, rosemary, garlic, basil, and catnip, found in essential oils, plants, or candles, acting as natural deterrents by masking host scents or being inherently unpleasant to them.
As our question: “Do coffee grounds attract pests?” — no! The opposite is true. According to the Environmental Protection Agency (EPA), coffee grounds are an efficient way to keep pests out of your garden.
Scattered coffee grounds are a great scent enrichment for many of our big cats! Rose enjoyed rolling around in them while Khan was trying to lick them up. Just like house cats…
For this reason, you should refrain from feeding coffee grounds to plants that need well-draining soil to grow. While used coffee grounds have a neutral pH of 6.5-6.8, they should still be avoided for plants like Ferns and herbs (Rosemary and Lavender) that thrive in neutral to alkaline conditions.
Dogs have a similar distaste for coffee grounds and bitter orange.
Don't Just Keep Odors At Bay, But Keep Pests Out, Too
Mosquitos, ants, slugs, and wasps are just a few common pests that are repelled by coffee grounds. Specifically, the nitrogen, caffeine, and diterpenes found in coffee keep certain insects away because of the toxic effects these compounds have on bugs.
Roaches may not be able to sip on coffee, but their affinity for it is likely as strong as the typical American. Cockroaches are attracted to the scent of fresh coffee grounds, making your Keurig, standard pot, or grinder prime real estate for these pests.
Mint: The strong scent of spearmint, peppermint, or pennyroyal can deter yellow jackets and wasps. Plant mint in your garden or use it in pots on your patio or porch. Marigold: Marigolds have a strong scent that can also repel these insects. Plant them in your garden or use them in pots around your home.
Dogs hate strong, pungent, or irritating smells due to their highly sensitive noses, with citrus, vinegar, spicy peppers, strong cleaning products (like ammonia/chlorine), alcohol, and some essential oils (like eucalyptus) being among the most disliked, often causing irritation or overwhelming their senses. While there's no single "most hated," citrus and vinegar are consistently top contenders for repelling dogs.
Though rodents are not attracted to coffee, they sometimes use burlap to make nests. Coffee warehouses must take measures to deter rodents because their excrement will damage coffee beans.
Kopi luwak, also known as civet coffee, is a coffee that consists of partially digested coffee cherries, which have been eaten and defecated by the Asian palm civet (Paradoxurus hermaphroditus).
Mice hate strong, pungent smells that disrupt their senses, with peppermint oil being a top choice, followed by other intense scents like clove oil, cinnamon, vinegar, ammonia, and cayenne pepper, which mimic predators or mask food sources, making them uncomfortable and prompting them to flee.