Coffee has undeniable benefits to the human body. They include: providing you with energy, promoting weight loss, preventing the risk of some diseases such as type 2 diabetes, supporting brain health, and lowering the risk of depression, among others.
However, it seems that coffee benefits aren’t limited only to the human body. Some gardening articles and blogs suggest that you can use coffee in your garden as fertilizer, for your compost, as a mulch for your plants, and to keep off snails and slugs.
However, there’s so much contradicting information on the internet regarding coffee grounds and plants. So the question remains, are coffee grounds really good for your garden, and will they hurt your plants? Read on for clarification.
Will Coffee Grounds Hurt Plants?
The short answer is yes. Coffee grounds will do more harm than good to your plants and garden. How? Coffee grounds contain a natural stimulant known as caffeine. While caffeine is why most people drink coffee, it is bad for your plants and garden. This is because it reduces the growth of plants in your garden. The caffeine in coffee grounds is a major negative factor that negates the positive effects of the minerals, nutrients, and acids in your coffee grounds. Let’s get into details.
Reasons Why You Shouldn’t Use Coffee Grounds in Your Garden
In this section, we’ll look at the common myths that are on the internet regarding the benefits of coffee for your garden and the reality about it. Let’s get started.
Myth: Coffee Grounds Can Be Used as Fertilizer and for Compost
As mentioned earlier, some garden articles and blogs will suggest that you use coffee grounds as fertilizer in your garden and for compost pits. This is because, coffee grounds contain minerals such as potassium, phosphorous, nitrogen, and other micronutrients that are thought to help your plants grow. Additionally, the nitrogen in the coffee grounds is said to make good green matter for your compost.
These articles and blogs will suggest that you sprinkle the coffee grounds in your potted plants, on the garden surface, use them as mulch, mix the coffee grounds with compost, and voila, your plants have the fertilizer they need.
The coffee grounds you use for your garden are bad for your plants. Firstly, coffee grounds are too fine to be used for mulch since the mulch turns out so compact that water cannot go through it to the plants’ roots. Usually, a mulch needs breathing – letting air in and out of the soil for plants to grow. When coffee grounds are used for mulch, the plants die due to dehydration. Therefore, don’t use coffee grounds as a mulch for your plants.
Secondly, your soil contains nitrogen that contributes to the plant’s growth. Adding coffee grounds to your soil can lead to a nitrogen overload that eventually restricts the growth of plants.
Lastly, adding coffee grounds to your compost will kill earthworms that are essential for plant growth. This is a result of the organic chemicals and compounds released by the grounds as they break down in your compost. Additionally, using coffee grounds in the garden kills helpful microbes present in the compost since coffee grounds have antibacterial properties.
Myth: Coffee Grounds in the Garden Are Good for Plants that Love Acid
Some plants such as azaleas, hydrangeas, rhododendrons, and lily of the valley, among others are acid-loving plants. So it’s said that adding coffee grounds to such plants will give them an acid boost.
First off, not all acid-loving plants will tolerate high amounts of acid. Additionally, it’s difficult to fertilize or compost your acid-loving plants in a vacuum, which means other plants are at risk of acid exposure. Equally important, you can’t permanently change the PH of the soil simply by adding something acidic. So, adding coffee grounds to the plants to boost acidity may be pointless.
Last but not least, used coffee grounds aren’t necessarily acidic. The level of acidity in coffee grounds depends on the origin of the coffee and how it was processed. And this also explains why different coffees will taste differently. Generally, it’s not clear how much acid is in used coffee grounds. Therefore, given the drawbacks of using coffee grounds for acid-loving plants, it’s not worth the risk.
Myth: Coffee Grounds in the Garden Will Keep Off Slugs
Some research suggests that using coffee grounds will repel slugs by creating a snail or slug barrier. This myth is based on a study involving highly concentrated caffeine amounts.
In essence, your used coffee grounds won’t repel snails or slugs in your garden. Additionally, the used grounds won’t even slow the snails down. In a study involving highly concentrated caffeine amounts sprayed directly on plants, it’s evident that caffeine kills snails or slugs. However, the caffeine used in the study is in high amounts compared to that present in used coffee grounds. Therefore, used coffee grounds won’t repel or kill snails.
Myth: Used Coffee Grounds Don’t Have Caffeine
Some people have the impression that used coffee grounds don’t contain any caffeine in them. They believe that caffeine is only present in fresh coffee grounds.
Used coffee grounds contain a significant amount of caffeine that is bad for your plants. Usually, caffeine kills off competing organisms that are present in the surrounding area (allopathy). Therefore, sprinkling coffee grounds in your garden or around your plants will suppress germination and plant growth.
Coffee Grounds and Gardening FAQs
Will Coffee Grounds Attract Rats?
Coffee grounds neither attract nor repel rats. However, if you have rats as pets, it would be best to keep coffee grounds away from them. This is because the caffeine in coffee may cause caffeine toxicity in rats which may lead to health issues.
Can Coffee Grounds Change the Flowers’ Color?
Some people believe that the acidity in used coffee grounds will change the color of flowers such as hydrangea. However, this is not true. The acid levels in used coffee grounds cannot change the soil PH, therefore, it’s unlikely they’ll change the flowers’ color.
Alternative Uses for Your Used Coffee Grounds
With all the drawbacks involved with using coffee grounds for your garden, compost, and plants, it’s not worth the risk. If you don’t want to throw away your coffee grounds, here are some alternative ways to use them.
- To neutralize odors
- Exfoliate Your Skin
- Scour Your Pans and Pots
- As a Natural Dye
- Tenderize Meat
- Repair Scratched Furniture
Caffeine in coffee grounds will inhibit the growth of plants. Therefore, coffee grounds shouldn’t be used in your garden or for compost. Research shows that caffeine was first a plant mutation that was accidentally passed on. Caffeine gave plants such as cocoa, coffee, and tea an edge over competing plants that grew nearby. Caffeine in these plants would inhibit the growth of other plants. Therefore, you shouldn’t use your coffee grounds as a fertilizer, mulch, or to repel slugs from your garden.