There is nothing quite like a fresh cup of coffee to start your day off right. As a plant owner, you may be wondering if you can use your brewed coffee grounds to fertilize houseplants.
Many people choose to use coffee grounds for an easy, ecofriendly, and cheap way to keep their plants thriving.
But are coffee grounds actually good for your houseplants?
Yes, coffee grounds are beneficial for indoor plants! This rich organic material is good for your plants due to its high nitrogen content, micronutrients, and high-water retention. The absolute best way to use coffee grounds on your houseplants is to compost!
Another good option is to use your coffee grounds in a homemade potting soil mixture. You can also use leftover liquid coffee to make a simple plant fertilizer.
Keep in mind that using coffee grounds will increase the moisture level of the soil. This is ideal for plants that thrive in moist soils!
But it is best to keep your coffee ground compost and potting soils away from plants that prefer dry soils such as succulents and cacti.
You should avoid directly applying raw coffee grounds to your indoor plants. Applying raw coffee grounds can increase the moisture levels in the soil too much. Which can negatively impact your plants growth in a few ways.
Understanding how to get the most benefits out of your coffee grounds will have your houseplants gleaning with vivacious thanks!
Read on to learn how to make the most of your morning ‘cup of Joe’ by incorporating coffee grounds into your houseplant care routine!
Benefit Of Using Coffee Grounds As A Houseplant Fertilizer
With all this talk of using coffee grounds you may be wondering what actually makes them a good option for your houseplants.
Besides being a great excuse to brew a fresh pot of coffee there are a few reasons why plant owners opt for coffee plant care. There are four main reasons plant owners love using coffee grounds!
1. Rich in Nutrients!
The two most important nutrients that plants need to survive are nitrogen and phosphorous. Amazingly, coffee grounds are high in nitrogen!
In fact, coffee grounds are made up of about 2% nitrogen by volume. Making them a great choice to ensure your plants are getting an added boost of sweet nitrogen nutrients.
Coffee grounds are also packed with a bunch of wonderful micronutrients that your plant will love.
Micronutrients such as calcium, magnesium, iron and more can all be found in coffee grounds!
2. Easy to Find!
Coffee grounds are extremely easy to find. You don’t have to go run an errand to the local garden shop or spend hours searching online just to find coffee grounds.
They are readily available and commonly found in most households. Even if you do not have any coffee drinkers in your home, a friendly neighbor (although a little confused at first) would likely be delighted to give you their used coffee grounds.
3. Ecofriendly!
Coffee grounds are something that most people consider garbage destined for a landfill.
Luckily, some very smart gardeners found a better use for them! Using coffee grounds in your plant care routine means that they will not add to the global garbage problem.
You will be taking what would be a contribution to environmental pollution and instead are utilizing them to enhance your plants.
This is also a natural way to improve your green family’s health without the use of synthetics.
4. Low-Cost Plant Care!
Let’s face it, gardening can sometimes be an expensive hobby. Any chance to cut down on cost is always welcome.
Plus, it means a little extra money to spend on more plants! Coffee grounds are a great option to reduce the cost of plant care.
Since they were going to be thrown away, it is an extremely economically efficient option that costs you nothing out of pocket.
It also means that you will likely have to spend less on other plant care products that you would have bought to achieve similar results.
This all sounds fantastic! But before you rush to throw coffee grounds on your houseplants, there are a few things worth considering.
When Coffee Grounds May Not Be The Best Thing For Your Indoor Plants
Not all humans enjoy a toasty cup of coffee or an iced caramel macchiato to start their day. And not all plants enjoy coffee grounds in their care routine.
Adding coffee grounds will increase water retention in the soil. This creates a moist soil environment.
All plants are unique in their needs. And it is always crucial to understand those needs if you want your plants to grow to their full potential.
Some species will thrive in moist soils, but others may become stressed. You should be aware of your plant species soil preferences and avoid using coffee grounds on plants that prefer dry soils such as cacti and succulents.
Another common blunder to avoid is incorrectly applying the coffee grounds. You should not directly apply coffee grounds to your indoor plants.
Although it seems like it would be beneficial it can actually harm a plants growth and cause stress. Coffee grounds are very good at holding in water.
When they are directly applied to the plant it can actually cause too much water retention. Putting coffee grounds around your plant may result in unwanted fungal growth from the excess moisture.
This direct application method can also lead to overwatering. With the extra water retention of the coffee grounds, your normal watering schedule could result in an unhappy, waterlogged houseplant.
In addition, directly applying coffee grounds can effect soil pH. Brewed, or used, coffee grounds are slightly acidic.
This acidity is not an issue when coffee grounds are integrated properly. However, directly putting them around your plant can slightly lower the soil pH which can harm certain species.
Not to worry! You can easily avoid the negative effects associated with coffee grounds while securing all of their nutrient rich benefits.
How to Use Coffee Grounds on Your Houseplants
1. The Best Way: Composting
If you want to get the most out of your coffee grounds you should compost them. For those of you who are not too familiar with composting, it may seem like an intimidating and complicated project.
But it is much easier than it appears! In reality, composting is pretty simple. Although some gardeners have turned it into an almost art form.
In general, composting uses “greens” and “browns”. “Greens” are things that are high in nitrogen, such as coffee grounds and eggshells. While “browns” are materials that are high in carbon such as paper and dried leaves. These are used with a roughly 3:1 ratio of “browns” to “greens”.
You throw your materials into a bin or a pile and give it time to breakdown. As long as you maintain around a 3:1 ratio you can use other materials, that would have otherwise been thrown into a landfill, for the compost.
It is not uncommon to find small composts in some gardener’s kitchens so that they can easily throw food scraps into the compost.
The result is a wonderfully nutrient dense growing material for your plants. This can be mixed into your regular potting soil or mixed into the top layer of already potted plants when it seems time for their soils’ nutrients to be replenished.
Since the coffee filter is paper it is considered a “brown” and can also be thrown into the compost!
This method extracts all of the rich nutrients of coffee grounds and serves them to your houseplants in the best possible way.
2. Enhance Your Potting Soil Mix
As mentioned earlier, coffee grounds are very good at trapping moisture. This can have adverse effects when directly applied.
But it can be a wonderful addition to a homemade potting mix! Water retaining materials, like coffee grounds, can be a great quality to have in a potting mix.
Just keep in mind you want to balance out all of the elements of your potting mix. So, adding coffee grounds to a mix may mean also adding a little more sand for drainage.
As a reminder, it is always important to understand each of your lovely plant’s preferences of soil type before potting.
Some plants, such as succulents and cacti, prefer dry well drained soil. But many plants enjoy a nice moist soil to keep them hydrated and comfortable.
If you have houseplants that fall into the second category, adding coffee grounds to your potting mix could be a great option! Not to mention a little extra nitrogen boost from the coffee grounds.
3. Coffee Fertilizer, Yum!
Another option is to use your leftover liquid coffee. Instead of throwing away that last bit of coffee that has been sitting in the pot all day, put it to some use!
Mix a 1:3 ratio of cooled coffee with tap water, and voila! You have made your own liquid fertilizer. For example, if you have ¼ cup of leftover coffee you would mix it with ¾ cup of water.
A word of caution, this will be an acidic fertilizer. Meaning that it will lower the pH of the soil. Some plant species prefer acidic soils, while others do not.
One very common houseplant that thrives in acidic soils is the African Violet.
Using this coffee fertilizer, no more than once a week will keep the soil pH low while replenishing some key nutrients.
Coffee and Soil pH
When discussing coffee focused plant care methods, it is important to understand how it can affect the soil pH.
Time for a super quick science lesson! The pH scale goes from 0 to 14 with 7 considered neutral.
The pH range of acids are 0-6.9, while bases range from 7.1-14. So, high acidity means a low pH (a little confusing I know). Understanding the basics of soil pH is important to maintaining your plants.
Most plants prefer a slightly lower than neutral pH because it allows for more nutrient uptake. However, there are dangers to going too low.
When soil pH goes too low It can expand the range of nutrient availability to toxic levels. Which can result in stunting plant growth.
Raw, or unbrewed, coffee grounds are highly acidic and should never be used on your plants.
Similar to raw coffee grounds, liquid coffee is also very acidic and should not be directly applied to a plant without first diluting.
Used, or brewed, coffee grounds run a much lower risk of lowering the soil pH too much.
But it is still good to be aware that they are slightly acidic and can impact your plants soil.
Final Thoughts
Plant owners opt for using coffee grounds in their houseplant care routine for a range of reasons. They are high in nitrogen and rich in various micronutrients.
Coffee grounds are commonly found in most homes making them a readily available material. Gardeners can feel a sense of pride that they are taking something that would have added to the landfill and instead using it to enhance their plants.
In addition, coffee grounds are an extremely cost-effective option.
Although there are many wonderful reasons to use coffee grounds, you should be conscious of the possible dangers. Do not apply coffee grounds directly to plants.
The extra water retention can lead to fungal growth, overwatering, and can impair growth.
The best way to optimize your coffee grounds is to compost them using a simple 3:1 “browns” to “greens” method.
Another option is to mix your coffee grounds into a homemade potting soil. Additionally, you can create a simple liquid fertilizer from leftover coffee.
Be aware that raw coffee grounds as well as liquid coffee fertilizer are very acidic and will lower the pH of your soil.
If you opt for an acidic method, such as the liquid coffee fertilizer, only use it on plants that enjoy low pH soils like the African Violet.
As with all plant care methods it is vital to fully understand each of your plant species unique care needs so that you can best help them flourish!
Written By
Amber Noyes
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.
Spreading the grounds on top of the soil invariably results in the growth of mold, picked up from the environment. It eats nutrients in the coffee. I don’t know if it can harm the plants or not, but looks ugly. Covering with more soil works. Could the tiny acidity be balanced out with ground calcium carbonate eggshells? Other people advise to use eggshells for plants, but call for an acid.