Last Updated on May 1, 2022 by John Moretti
If you are a regular coffee drinker, you will know just how quickly coffee grounds can pile up. Instead of throwing used coffee grounds out, you can put them to good use, especially if you have houseplants. You can use old coffee grounds to fertilize your plants!
The best way to use old coffee grounds for indoor plants is to add them to compost and use that to make compost tea. Compost tea is an excellent tonic for your plants, providing nutrients and repelling pests. You can also add a thin layer (1/2 inch) of coffee grounds directly to the soil as a mulch.
One does have to be careful about how you apply coffee grounds to your house plants because they can cause more harm than good. Here, we discuss the different ways to use coffee grounds for your indoor plants and when you should avoid using coffee as a soil amendment.
How To Use Coffee Grounds To Benefit Indoor Plants
For organic gardeners, used coffee grounds are a valuable resource. Even if you have just a few house plants, it is well worthwhile to collect up your coffee grounds and use them to benefit your houseplants. It is a fantastic way to recycle your coffee grounds so that they do not end up in a landfill.
There are different ways that you can add coffee grounds to plants’ soil. Some ways work better than others.
Sprinkle Coffee Grounds On The Soil Surface
This is a method you may have heard before. Many people recommend simply adding coffee grounds to the surface of the soil as a mulch.
In theory, it’s a good idea because coffee grounds are good at retaining moisture, so make an effective mulch. However, if the layer of coffee grounds is too thick, it traps moisture and can lead to fungal diseases.
If you do just want to add coffee grounds directly to the soil, do so very sparingly. Apply a very thin layer of coffee grounds to house plants – less than ½ an inch thick.
Add Coffee Grounds To Compost
A better way to utilize coffee grounds is to add them to your compost heap. Mixing the coffee grounds up with soil and other organic matter will ensure it does not cause fungal growth and will benefit plants more significantly.
Earthworms eat the coffee grounds, and as they pass through their digestive tract, they are turned into rich compost. Coffee grounds contain high levels of nitrogen, so while they are brown in color, they are green matter in composting terms.
When you add coffee grounds to your compost pile, you must also add four times as much brown matter (by weight, not by volume). Dried leaves, shredded newspaper, straw, or sawdust all count as brown matter.
It is important to add a wide variety of things to your compost heap to promote good soil health. Coffee grounds should make up at most 20% of the material you compost.
Use your homemade coffee ground compost when you repot your houseplants. The compost releases nutrients into the soil gradually, making it a much more effective fertilizer than chemical plant feed.
Make Compost Tea For Indoor Plants
To get even more benefit out of coffee ground compost, you should make your house plants a nutritious brew of compost tea.
- When your compost is finished (smelling earthy, looking dark and crumbly), add equal parts water and compost to a bucket.
- Allow the mixture to sit in the bucket for 24 hours, giving it a stir every few hours.
- Use cheesecloth or a mesh colander to separate the liquid from the solids – the liquid is the compost tea.
- Give your indoor plants a thorough watering with the compost tea.
The Best Way To Use Coffee For House Plants
Composting coffee grounds and then using them to make compost tea for your house plants is definitely the most effective way to fertilize plants with coffee.
Coffee ground compost tea is beneficial to plants in a number of ways:
- It boosts plants’ immunity to pests and diseases.
- Increases plants’ overall health and growth rate.
- Reduces the need for other fertilizers.
- Increases the soil’s water holding capacity.
- Improves the structure of the soil, improving soil health.
A Word Of Warning About Coffee And House Plants
Coffee grounds can harm plants if they are not used appropriately. As mentioned earlier, if you simply add coffee grounds to the soil surface, they become compacted, trap a layer of moisture against the soil, and cause fungal outbreaks.
Coffee grounds are high in nitrogen. They have an NPK ratio of about 2.1:0.3:0.3. If you add them directly to plants in too high quantities, the plants can suffer from nutrient burn.
Another property of coffee grounds is that they are acidic. You have to be mindful not to add too much coffee grounds to the soil because you do not want to lower the pH to the point that is detrimental to plants.
Because coffee grounds are so good at retaining water, adding too much to your houseplants’ soil can increase the risk of overwatering. Be sure to mix some perlite into the potting mix along with the coffee ground compost to improve drainage.
Coffee contains caffeine, which can stunt young plants’ growth. Do not use coffee ground compost for starting seedlings.
Can You Water Plants With Leftover Coffee?
If you have a little coffee leftover from your brew, you can use it to water your acid-loving houseplants like Dieffenbachia, African violets, and moth orchids. Only do this once a week to prevent making the soil too acidic.
It is a good idea to dilute the liquid coffee with water before using it for your house plants. Keep an eye out for signs of nutrient burn – yellowing leaves or crispy leaf margins.
Rather than just sprinkling your used coffee grounds on top of your house plants’ soil, add it to your compost pile and then use it for your house plants. Composting coffee grounds first prevents the high nitrogen and caffeine levels in fresh coffee grounds from harming plants.
Use coffee ground compost to make nutritious compost tea for your house plants. You should definitely see an increase in their growth rate and notice their increased resistance to pests and diseases.