When looking for the perfect fertilizer, you may come across the idea that used coffee grounds can be used to help plants grow. This is a fantastic idea as you may be able to fertilize your garden with something that you throw in the trash every morning.
Lightly spreading used coffee grounds on the soil in your garden can give your plants another source of nitrogen, helping them grow. However, used coffee grounds can be too acidic for some plants, so mixing them with other materials is recommended to help dilute them. Azaleas love this.
If using coffee grounds as fertilizer intrigues you, then keep reading. In this article, we’ll explain why and in what scenarios you’d want to put used coffee grounds in your garden and other uses for used coffee grounds.
How to Use Coffee Grounds as a Fertilizer

Adding coffee grounds to your soil as a fertilizer adds organic material that helps improve drainage, water retention, and aeration in the soil. It is also a more sustainable method than dumping them in the trash or down the garbage disposal.
Used coffee grounds will also help microorganisms that are beneficial to your plants’ growth thrive, and they will also help to attract helpful earthworms to add essential nutrients to your soil. This is because the coffee grounds contain nitrogen, potassium, and phosphorus that will release into your soil.
To use coffee grounds as fertilizer:
- First, make sure to rinse them to help remove their acidity.
- Then, sprinkle them thinly onto your soil or add them to your compost heap. Make sure to balance them with carbon-rich materials such as dried leaves, woody prunings, or newspapers.
- Also, ensure you’re only using light amounts of coffee grounds. Using too much can cause them to clump together, creating areas in your garden that water can’t get to.
You can also turn your used coffee grounds into a spray to use on your plants. Simply add 2 cups of used coffee grounds to a 5-gallon bucket of water. Let this mixture sit overnight, and then it’ll be ready to put in a spray bottle for use.
How to Compost Your Coffee Grounds
Another great way to use previously used coffee grounds is to put them in your compost bin and use them as compost material. To go into the basics, compost material comes in two different types: green and brown.
Green compost material is rich in nitrogen, while brown compost material is rich in carbon, and you must balance this so you have both material types in your compost. You should keep a 4 to 1 ratio of brown to green compost material.
Coffee grounds are green compost material, so balance them with brown compost material, such as dry leaves or newspaper. If you use paper coffee filters, these can also be composted as green compost material.
There are some easy signs to recognize that can tell you if your compost bin is unbalanced. For example, if your compost pile smells bad, you have too much green compost material. You have too much brown compost material if your compost pile does not retain heat.
What Are Some Other Ways I Can Use Coffee Grounds?
If you still have some leftover coffee grounds, there are other ways to get use out of them. Here are a few other ways to use your used coffee grounds.
Feed Them to Your Worms
If you have a worm bin, coffee grounds are a great additive to help your worms. Just add about a cup of rinsed-off coffee grounds to your worm bin once a week. Just make sure you don’t add too many.
Even though rinsed-off coffee grounds reach a near neutral pH of 7, it’s still just a little below 7, typically hitting around a pH of 6.5. This means that if you use too much, you’ll hurt the worms by making the soil too acidic.
Add Them to Plants That Love Acid
As we just went over, used coffee grounds are typically slightly acidic, hitting an average pH of 6.5. However, used coffee grounds have already lost a lot of their acidity. New coffee grounds have even more acidity, making them perfect for acid-loving plants. These include azaleas, hydrangeas, blueberries, carrots, and radishes.
This is a good way to get use out of coffee that is going bad or coffee that you bought and then didn’t like. However, it is important to note that new coffee grounds still contain caffeine, which can harm some plants.
Make sure you do not use coffee grounds on any seedlings or young plants, as this will stunt their growth. It is also worth noting that you shouldn’t spread caffeine anywhere any pets you may have can get to.
What are the Benefits of Adding Coffee Grounds to Your Garden?
The main thing you’ll want from coffee grounds in your garden is their nitrogen content. Plants use nitrogen to complete most processes, including making amino acids, proteins, and DNA.
Coffee grounds are approximately 1.45% nitrogen. They are also good sources of magnesium, calcium, potassium, and other trace minerals. These are all things that plants can use to help them grow.
As previously mentioned, used coffee grounds can also attract earthworms to your garden. This is because the earthworms are attracted to the nutrients in the coffee grounds. Therefore, you definitely want earthworms in your garden as they highly benefit your garden’s productivity.
Earthworms constantly disturb your soil, creating better drainage and a more stable soil structure. It is also worth noting that they excrete even more nutrients for your plants to use. So even if you don’t want to use coffee to attract them, you likely want earthworms in your garden.
When Should You Not Add Coffee Grounds to Your Plants?

The main thing you need to worry about is the coffee grounds’ natural acidity. Unfortunately, many plants do not respond well to acidity and, even worse, to caffeine.
For this reason, you want to wash off and mix your coffee grounds with other fertilizer materials. This will naturally dilute the coffee grounds’ adverse effects while still getting their nutrients into your soil.
Pets
Another case where you might want to keep from using coffee grounds is if you have a dog. Caffeine can be harmful to dogs, especially in high enough doses. If you have a dog that loves to eat random stuff it finds on the ground, you may want to find something else to use as fertilizer.
Pests
Apparently, there is a widespread idea that coffee grounds in your garden will keep slugs and ants away. But unfortunately, this is just not true.
Studies have shown that even though slugs and ants do not like coffee grounds, they will still walk over them if they see something they like on the other side. So if you dream of using coffee grounds to keep away pests, you may want to think twice.