Both used and fresh coffee grounds contain nitrogen, potassium, phosphorus, and tons of micronutrients, and can be used in your garden as mulch or a slow-release fertilizer. Adding coffee grounds to soil improves drainage, water retention, and aeration.
Excessive acidic soil can kill or hamper the growth of plants like asparagus fern, Chinese mustard, Italian ryegrass, lavender, orchids, rosemary, tomatoes, and geranium. The roots of these plants are also not potent to absorb the nutrients added by the coffee grounds in the soil.
There are a select few plants that can benefit from fresh grounds—including acidity-loving Hydrangeas, Rhododendrons, Azaleas, Lily of the Valley, blueberries, carrots, and radishes—but generally, most common houseplants will prefer low to no acidity.
How Often Should You Add Coffee Grounds to Plants? You can fertilize houseplants an average of 7 to 10 days in a row, but no more, as there is a risk of over-acidification of the soil. A cup of ground coffee should be added to the compost once a week.
Not all plants are receptive to soil mixed with used coffee grounds. Take, for instance, your vegetable garden. If you grow your own food and want yours to thrive, you'll avoid adding coffee grounds by themselves directly to it.
Coffee grounds are highly acidic, they note, so they should be reserved for acid-loving plants like azaleas and blueberries. And if your soil is already high in nitrogen, the extra boost from coffee grounds could stunt the growth of fruits and flowers.
While many budding gardeners may be concerned that coffee grounds can attract pests, the reality is quite to the contrary. In fact, when implemented correctly, coffee grounds can be an effective way to repel certain pests such as wasps, snails, and mosquitoes.
Since coffee grounds have such a pungent and intense smell, mosquitoes do not like to come near it. Mosquitoes are repulsed by all types of coffee, whether it is fresh, used, or burnt. The most effective way to use coffee grounds for mosquito control is by burning them, as it creates a stronger aroma.
Don't just pour it down the drain — you can use it to fertilize your plants, both indoor and outdoor. Coffee grounds (and brewed coffee) are a source of nitrogen for plants, producing healthy green growth and strong stems. Coffee also contains calcium and magnesium — both of which are beneficial to plant health.
Yes, it's possible, but it should not be more than a thin sprinkling. If you add too much, the coffee grounds will form a dense layer on the surface of the potting soil that is impenetrable to water. On a regular basis, using leftover coffee to water your potted plants is a much better idea.
Eggshell Benefits
As it happens, eggshells can provide all the calcium carbonate the soil needs, which helps to lower the soil's pH level and make it more alkaline as opposed to acidic. This is incredibly beneficial for plant growth because many plants prefer to grow in soil that has low acidity.
Which plants shouldn't you try this with? Don't add eggshell fertilizer to plants that prefer acidic soil, like blueberries. Ericaceous plants such as mountain laurel, pieris and azaleas also fall into that category. In extreme cases, low acidity for plants could impact their overall health and/or the resulting crop.
Coffee Grounds to Deter Pests
Coffee grounds are commonly used to keep animals including slugs, snails, rabbits and fire ants from eating plants in the garden, and to keep cats from treating garden beds like litter boxes.
In the wild, the civet "cat" is naturally drawn to the best, ripe fruits on the coffee plant; that's why, effectively, they would produce the best beans, in small batches. A coffee "bean" is actually the seed of a cherry-sized fruit that grows on the coffee plant. Civets eat the whole fruit.
The green fungus called Trichoderma, is very beneficial to the soil. The blue-green fungus is moderately beneficial. At any rate, moldy coffee is good to use directly in the garden, on your houseplants, or in the compost pile.
The organic contents of cinnamon are perfect for increasing the root growth of plants. This spice's auxin content works to help the stem cuttings or seedlings sustain growth, all while protecting the plant with its antimicrobial and anti-bacterial qualities.
Using grounded coffee in garden lawns is a common practice to make plants grow faster. However, coffee also contains other ingredients like potassium and phosphorous, which are known to enhance plant growth.
Like any type of fertilizer, coffee grounds are only effective when used sparingly. It is never a good idea to add too much, as that could do more harm than good. The proper proportion is usually around 4 to 1, or twenty-five percent of coffee grounds to mineral soils by volume.
You may love your morning coffee, but ants could do without it. Another natural way to deter ants, sprinkle coffee grounds outside and around your garden. The smell repels them and they'll be looking for a less caffeinated place to hang out. Want to keep your home clean and clear of ants?
As such, some websites suggest placing coffee grounds around your home to keep roaches away. However, in a 2020 study published in the International Journal of Science and Healthcare Research, researchers tested this out and found that coffee grounds were not very effective at repelling cockroaches.
Mosquitoes hate the smell of lavender, citronella, clove, peppermint, basil, cedarwood, eucalyptus, peppermint, lemongrass and rosemary. They also hate smells such as smoke, for further insight, see our exploration on, does smoke keep mosquitoes away?
Coffee's bitter compounds are responsible for its repelling effects. These compounds make the coffee unpalatable to rats and mice. They will avoid areas where there is the use of coffee grounds.
Coffee Grounds
Not only do coffee grounds smell good, but they also work wonders when it comes to warding off unwelcome guests such as spiders.
“the smell of the coffee repels snails, slugs and ants. You may also have success using coffee grounds to repel mammals, including cats, rabbits and deer.”