If you drink a cup of coffee every morning and garden, you have a secret weapon up your sleeve: coffee grounds! Some coffee shops even offer their customers discarded coffee grounds for their gardens.
Coffee is highly nutritious for plants as it adds organic matter to the soil. While they won’t benefit from the caffeine the way we do, they will benefit from the extra nitrogen coffee adds to the soil. In a way, coffee is a lot like ordinary compost – except it breaks down much faster and won’t attract bugs.
Coffee works as a natural repellant for most animals. Cats, dogs, and many other mammals or microorganisms don’t like the smell! You can satisfy your plant’s nitrogen needs and keep them from being dug up.
Here, we’ll explore everything you need to know both about using coffee grounds to support plant growth and using coffee grounds to break down organic materials (like food scraps, veggies, dried leaves, grass clippings, and other green compost items beloved by earthworms) in your compost pile.
Coffee Grounds For Plant Growth
Different plants thrive in different types of soil, which is why organic gardening is not straightforward. You can’t just sprinkle coffee grounds on just any plant and hope for the best.
Acid-loving plants can benefit greatly from coffee grounds being added to soil or used under mulch around the base of the plant’s stem. Alkaline-loving plants, on the other hand, won’t likely react as well to used coffee grounds as fertilizer.
To know how to serve your garden best, you first need to differentiate between which of your plants love acidic soil and which plants thrive in a more alkaline environment. You might also find our guide on can dogs have coffee ice cream useful.
Although it’s not always clear how much caffeine is left in coffee grounds, most plants don’t like caffeine. This is why it’s always better to use spent coffee grounds. If you have expired coffee, it’s best to brew, discard the coffee, and keep the grounds.
You can also opt for decaf. The grounds should still be damp as otherwise; they can repeal water, leaving your plants thirsty.
What Plants Like Coffee Grounds?
The following plants thrive in acidic soil and, therefore, like coffee grounds:
- Mountain heather
- Mountain ash
Many fruit and veggies thrive in acidic soil, as well as many trees, but not all of these types of plants do, so take it on a case-by-case basis. The pH level of the soil allows these plants to better absorb the appropriate micronutrients they need to be healthy. Coffee is also a source of nitrogen, magnesium, potassium, and phosphorus, which are important nutrients for plants.
Keep in mind that if the soil pH is too acidic, it will harm your plants, even if they typically prefer acidic soil. For example, although tomatoes like slightly acidic soil, too much coffee can clump together and inhibit water from reaching the roots, which halts germination. So, less is more until you find the perfect balance.
What Plants Do Not Like Coffee Grounds?
We do not recommend using coffee for these plants:
- Cherry blossoms
While some of these plants may still grow in soil treated with coffee grounds, they’re likely to live longer and grow stronger when provided with alkaline soil in the garden. If the nitrogen content of your soil is already quite high, then adding coffee grounds can inhibit the growth of flowers and fruit. So these plants are better cared for with plant food.
For example, clover generally prefers to grow in soil that is free from or low in nitrogen. Plus, the hard coffee grounds also change the texture of the soil, which makes it harder for some plants to grow.
Coffee Grounds For Indoor Plants
Fresh coffee grounds can also be good for indoor plants in potting soil. Since you don’t need to ward off pests, you might not need as much as you would with outdoor plants. In particular, since indoor plants can struggle with drainage, coffee grounds can help with maintaining proper water retention and aeration.
It’s much easier for houseplants to run out of nutrients as the soil is unlikely to be changed. Outdoor soil naturally gains nutrients from the decomposition process or from weathered rocks and stones. Although coffee grounds for houseplants are not a substitute for plant food, they do help to keep your plants nourished.
The following houseplants thrive with added coffee grounds:
- Jade plant
- Snake plant
- Christmas cacti
- Spider plant
- Peace lilies
Most cacti and succulents like acidic soil, so they are happy when coffee grounds are used to fertilize them. Just ensure the process of adding coffee does not result in overwatering. How To Use Coffee Grounds In Your Garden.
Applying used coffee grounds to your garden as fertilizer for your plants is a simple process:
- After you’re done making coffee in the morning, allow the coffee grounds to cool to room temperature.
- Sprinkle a light layer of coffee at the base of your acid-loving plants.
- You can work them into the top layer of the soil using your hands or using a small garden trowel.
- Then, you can cover the coffee grounds with a light layer of mulch to ensure that they stay moist. If coffee grounds dry out, they can repel water, so they must be covered with organic material.
- Remember, it’s ok to troubleshoot whether you’re using coffee grounds as a pesticide or solely as fertilizer. Trying coffee on different types of plants, changing up the caffeine content by using decaffeinated coffee grounds, or switching up the number of coffee grounds you use in the soil can all make a difference. In addition to creating a more acidic environment for your acid-loving plants to thrive, adding coffee grounds to the soil also:
- Improves the soil structure, helping the roots to take and keep a stronghold in the ground
- Works as a repellent for many pests, including slugs and snails
- May inhibit the growth of weeds around the plant’s base
What Kinds Of Coffee Are Suitable For Plants?
You should only use black coffee or plain coffee grounds on your plants. Just dumping leftover coffee into your house fern isn’t the best option in most cases – nor would whole coffee beans be any good.
Added sweeteners are not suitable for plants. They can also attract bugs like ants, which can then attack your plant. Dairy should never be composted or added to the soil.
It can attract bugs of all sorts, like gnats and flies. It can also harbor some pretty nasty bacteria when you just let it sit out – even if it’s sitting in your plant’s dirt.
Can You Put Coffee In Potted Plants?
Yes. If you follow all the guidelines we’ve discussed above, you can efficiently utilize coffee in most potted plants.
Just be sure you’re ready to deal with the drainage. You probably don’t mind leaving water sitting around in a drainage pot for a bit – but coffee is another story!
Of course, you don’t want to use it on all plants. Some don’t like the acid that coffee brings to the soil, which can cause serious problems. This is because coffee tends to get concentrated faster when used in a pot since there is limited soil to soak it up.
I recommend using coffee less on potted plants, though the exact amount will depend on the type of plant. It’s better to add too little than to oversaturate the soil and kill your plants.
How Often Can You Water Plants With Coffee?
Generally, I recommend only watering your plants with coffee once a week. With that said, I also recommend checking your plant’s favorite soil type and keeping an eye on its condition. Some plants love coffee, while others will take a turn for the worst as soon as the fumes hit their leaves.
Outside, coffee causes less of a problem. There is more soil to soak it up and spread it out. Inside, potted plants can be overwhelmed by the downsides of coffee much faster.
Start by adding coffee grounds sparingly. You can use a thin layer just under the top of the soil. Don’t add any more until the coffee is completely gone. This process will likely take a month or so.
Burying coffee grounds is particularly useful for keeping pests out of your garden, and it also brings nutrients back into the soil.
Coffee Grounds For Compost
You can also use coffee grounds to help break down organic plants and other materials in your compost pile. This isn’t just good for the environment — it’s convenient for you as well.
Be sure to check the label of the coffee filters you’re currently using to find out whether you can simply toss them into your compost pile as well. Many coffee filters today are compostable and work well as a carbon source for your compost pile.
It’s important to add a carbon source, known as brown material (you can use dry leaves if you don’t have compostable coffee filters) when you add used coffee grounds, a green material, to your compost pile.
To successfully add coffee grounds to your compost pile:
- Layer leaves, grass clippings, and coffee grounds (in that order), and turn weekly.
- You can also simply add coffee grounds to the compost pile you already have in your yard.
- Going through coffee grounds faster than you can compost them, or want to save them for a future compost pile? Store them in a large plastic bag. If the grounds develop mold, no worries — it will be decomposed during the composting process.
Used grounds are also suitable for vermicomposting, as you can add the coffee grounds to your worm bin. If you don’t have a compost pile but rather a compost bin that is collected by a service, then the likes of coffee grounds or eggshells should be fine too.