Are used coffee grounds good for houseplants? The short answer is yes! Many houseplants benefit from coffee grounds being used to fertilise or feed them. However, just as some people like coffee, some plants do like coffee and others don’t. In the first instance, you might be thinking a bit odd to sprinkle cappuccino on the soil at all. Then again you might also think it odd to be giving your discarded eggshells to your plants, but plenty people swear by it!
For gardeners who drink coffee, it can be a good idea to use coffee grounds as a treat for indoor plants as well as those in a greenhouse or garden. But why is this?
Here, we’re going to take a close look at the nutritional value of giving your plants your used or fresh coffee grounds. We’ll also explain how to prepare and use coffee grounds to feed them with. Finally we have listed some of the plants which respond well to coffee grounds – and others who may suffer from a serving!
What are coffee grounds?
Nice and simple – coffee grounds are the leftover residue you’ll find when you’re done with making your morning drinks. More often than not, we end up throwing these away!
Coffee grounds and residue make up a sludge-like matter that still retains a brown colour and some flavour. Instead of throwing these grounds away, however, we can recycle those grounds to help cultivate plants.
Bizarrely enough, many people actually use coffee grounds to help fertilise their houseplants – but how well does this work in practice, and is it worth swapping from traditional fertiliser to used coffee? Are coffee grounds good for indoor plants in general?
Why do some plants like coffee grounds?
Some plants benefit from a liquid dressing of coffee grounds to help them grow – just as with any fertiliser, care must be taken regarding its strength, and the frequency at which it is given.
Some plants tolerate a stronger solution than most – but in general, the liquid from coffee grounds is safe at a ratio of one part coffee to nine parts water (more on that a little further down).
Other plants that aren’t so hardy can be treated with an application of coffee grounds in a mulch. This is a great way to share health supporting nutrients. Plants who need a little perking up can show visible improvements after only a few feedings of coffee!
Whichever way you administer coffee ground material, try to memorise the ‘before and after’ appearance of your plants – it’s a great way to work out whether or not the process is worth repeating.
Why not take a photo of your coffee-fed plants at intervals of three months? Remember that it will take a few feedings for results to start showing. This may be as subtle as flowers lasting longer, for example – and perhaps leaves and stems start looking stronger, too. Sometimes, even colours can appear more vibrant! This is usually more noticeable on leaves, and due to photosynthesis.
How can coffee grounds be used to help houseplants?
There are three main ways in which coffee grounds can be used to help cultivate plants. There are a number of plants that benefit from coffee grounds being used to fertilise or feed them – either through a liquid form, a mulch, or directly dug into their compost.
If you want to travel the liquid route, be sure to take caution. Watering with liquid from coffee grounds needs to be well diluted. You shouldn’t give coffee solutions to your plants at every watering, either – once or twice a month is sufficient for most plants. In fact, they may not be able to handle more than this!
Just as some humans prefer strong coffee, most plants only cope well with weak coffee. You risk overloading them by offering too strong a solution – at worst, it could kill them! However, there are things you can do if you’re worried you’ve overdone it.
Mulching coffee grounds for your houseplants
Mulching is a simple way to bring together spent coffee grounds. Mulching coffee granules can be as simple as lifting them from your coffee machine or press, and when cooled, applying them to the base surface area surrounding a plant. Several organic materials can be mixed to form a mulch, too!
Composting coffee grounds for indoor plants
Composting coffee grounds involves combining them with other organic matter. Usually, the mixture is left to break down before being distributed around plants. Alternatively, it may be mixed with soil or other compost and left to mature for use at a later stage.
Follow the gentle coffee grounds ratio as mentioned above, and you can easily prepare special compost with the added boost of bean brew!
What nutrients are found in coffee grounds?
You’ll regret throwing those coffee grounds away! While they aren’t exactly appetising to us, they are still rich in wonderful nutrients.
Nutrients in coffee grounds include nitrogen, potassium, phosphorus, carbon, chromium, magnesium, calcium and iron. You’ll also find caffeine and diterpenes in ground coffee – and it’s these elements that are most important for your indoor plants!
Why is caffeine from coffee grounds so good for some plants?
Caffeine is a stimulant that affects plants as well as humans (and don’t we know it!). Believe it or not, a gentle dose of caffeine can help to encourage photosynthesis – it’s true! It is also instrumental in helping plants absorb water and other nutrients from soil. Caffeine is known to lower the PH level of soil, too. However, it’s really important to make sure you don’t overdo it on the caffeine front – or your plants might die.
What are Diterpenes, and why are they so important for plants?
Diterpenes are made up of four isoprene units – which are basically chemical compounds. Diterpenes are found in the inner systems of most marine life, land animals, bacteria, fungi and plants. They have an anti inflammatory function and form compounds such as retinol and phytol. In plants, phytol is vital for photosynthesis!
What’s really fascinating is that research has proved that diterpenes are carried in the oil of coffee beans. Therefore, it pays to carefully feed your blooms with the odd bit of Joe!
How can I tell if coffee grounds are helping my plants?
The nutrients in coffee grounds are beneficial to many plants when consumed in a concentration they can cope with. Evidence of a successful application of coffee grounds to give plants a boost may take time to see, however – so be patient!
Simple signs to look for may include leaves looking to be in better shape, perhaps more evenly formed and not falling off so easily. They may seem a little larger and in some cases, form more quickly. Flowers may become slightly larger, and there may be more of them budding forth over time.
Buds may become more robust, and again, pop up in greater numbers. Sometimes, weaker plants do not support all the buds they produce to a flowering stage. You may have seen buds fall before flowering with apparently no reason, for example – case in point, plants in good conditions do not do this!
Are coffee grounds toxic to plants?
Giving plants a too concentrated dose of coffee grounds can be toxic and put them under strain. The result of such stress can result in withering leaves, wilting, and/or changing colour. Leaves may fall off, flowers may become deformed and/or fall off, and in worst cases, plants die.
What’s worth noting is that coffee grounds can affect alkaline and acidic plants differently. First of all, let’s consider what the terms ‘alkaline’ and ‘acidic’ mean when it comes to your plants.
We know that soil and compost have a PH level of measurement. Various elements in soil contribute to it becoming as alkaline or acidic – with 0 PH as a base figure, 0 to 7 is considered acidic and 7 to 14 is alkaline. As hydrogen ions increase in the soil, the pH level decreases.
For easy reference, it’s safe to consider that most garden plants survive well with a pH level of approximately 6.5. Therefore, they are most commonly slightly acidic.
To make your coffee grounds completely neutral, consider washing them before you give them to your plants – this shouldn’t have any kind of effect on the PH of their soil.
How should I prepare and serve coffee grounds to plants?
If you are preparing coffee grounds especially for plants, simply brew them in the same way as though you were preparing a coffee drink for yourself. Do not add milk or sugar, and allow the drink to cool.
Milky coffee should never be given to plants. It can encourage bacteria to develop and fungus to form! You can dilute coffee made for human consumption – adding additional water will make it more viable as liquid feed.
If you are going to use the coffee grounds as a mulch, stir them well and allow them to cool. Apply them directly to the surface of the container housing your plant, or to the surface of plants in the soil.
Do not allow the granules to touch leaves and roots. You may need to grate the soil or other material on the surface near the base of plants to allow your mulch or compost to be most effective. This means ensuring the nutrients from granules can leak down through any existing surface material.
Preparing coffee grounds in compost is easy! Simply scatter them over your compost and then mix them in. In dry climates, compost can dry out near the surface and mixing wet grounds may seem harder.
It may be a good idea to skim the top off your compost and spread some compost over a greater surface area. Then, layer on the coffee grounds and cover them up before forking the whole heap to mix up materials. Organic mixtures such as this are nutrient rich and suit many plants.
A useful tip is to create a compost heap for acid loving plants and another for alkaline loving plants. It really is the best way to ensure you don’t deliver some nutrients to a plant that can’t use them, or worse, becomes poisoned by them.
You can test the PH in soil and compost with testing strips – readily available online, and easy to use.
What should I do if I overload my plants with too strong a solution of coffee?
- If your plants are in well-draining pots, first lift the pot or container out of the water collection saucer. Don’t allow the plant pot to sit in a bath of fluid.
- Do not be tempted to saturate the plant with clean water, either. That could cause root damage, root rot and overload the plant.
- Do not be tempted to turn up the heat. The plant may suck up more fluid at a faster rate in warmer temperatures. Your aim is to slow it down!
- If possible, soak up excess surface moisture with tissue. Don’t press down on soil or compost from the top because you risk compressing the roots and soggy soil or compost.This will compact soil or compost and could damage roots by putting them under too much pressure.
- Leave plants in an airy space and don’t water them until you have allowed extra time to dry out.
What houseplants like coffee grounds?
There are some plants that respond better than others to coffee grounds. Again, it’s all to do with that all-important PH, and the difference between acidity and alkalinity.
Roses, hostas, azaleas, strawberries, blueberries, carrots and radishes, for example, are some of the plants which thrive on coffee grounds.
It’s important to remember that coffee grounds are close to being neutral on the scale of PH levels. When used, they are slightly acidic. This is more relevant for house plants and plants in confined spaces such as gardens or greenhouses.
Humidity and general rainfall affect the intensity of some chemicals’ interaction with plants outdoors. What’s more, roots in pots and containers are closer to the soil, and therefore get their nutrients naturally from the ground.
As mentioned, when it comes to adding coffee grounds to your indoor plants, you should make the point of washing them with clean water – this will help to protect the PH of your soil.
What houseplants dont like coffee grounds?
Regardless of PH, however, there are always going to be a few plants that simply don’t do well with coffee ground. Plants that don’t enjoy having coffee grounds around include geraniums, pelargoniums, lavender, rosemary, black eyed susans, yuccas, orchids and tomatoes. This list isn’t exhaustive, so make a point to check your individual plant’s needs before you feed them coffee.
Frequently Asked Questions
Is it ok to give warm coffee grounds to plants?
No, it is best to use coffee grounds that are left over from being brewed and cooled. Coffee grounds at room temperature may be better delivered from the saucer upwards to roots, rather than from on the surface of soil or compost at the top of a pot.
Do not be tempted to put hot coffee grounds in a saucer or at the bottom of the container! They can take a long time to cool down, and you may damage roots as well as destroy some nutrients in the compost or soil.
Are grounds from decaffeinated coffee better for plants?
Decaffeinated coffee has useful nutrients for plants and it can be used in the same way as normal coffee. Decaffeinated coffee is, however, not considered better for plants. The only reduced or missing element is caffeine – otherwise, it usually contains the same elements as normal coffee.
Is granulated coffee the same as coffee grounds?
No, granulated coffee usually refers to the dry form of coffee, prior to being made into a drink. Coffee grounds are the residue of mushy wet matter which sink to the bottom of a coffee pot.
Do coffee grounds kill pests?
Coffee grounds are repulsive to some pests! This is a definite spin off benefit! Slugs just can’t seem to stand the smell or texture! Spread these around the base of plants and fruit trees or shrubs to deter unwanted visitors! Snails will back off from climbing up plants with coffee grounds in their vicinity.
Using coffee granules is a cost-effective, bio-friendly way to help some of your plants develop well while indoors. It’s a cheap, effective means of recycling a natural product that you’d normally throw away!
Are coffee grounds good for houseplants long-term? Yes – providing you offer them an occasional feed. It’s never a good idea to load up your plants with coffee grounds every time you water them, as you’re at risk of overwhelming them. Be sure to prepare your coffee grounds carefully, wash them with clean water to reduce the PH, and then apply in liquid, mulch, or compost.
Who knows – with a little coffee here and there, your fantastic indoor plants may soon start to take to new heights – be sure to document their journeys and keep coming back to your coffee grounds if you’d normally cast them into a bin.