Coffee grounds as fertilizer: uses & benefits
Coffee grounds are a popular home remedy for fertilizing orchids, roses and the like. We show why coffee is good for your plants and how to use it.
Coffee grounds are an excellent fertilizer for many plants [Photo: Monthira / Shutterstock.com]
Many of us don’t really get going without our morning coffee. But have you ever thought that you could also use the coffee grounds to give your plants a boost of energy? We will show you what else is in your coffee grounds and how it can support us in the garden.
Every German drinks an average of 165 liters of coffee a year – there are plenty of coffee grounds. The coffee grounds are the substance that remains in the filter after coffee has been prepared. There are many different uses for coffee grounds, but most of them just throw it in the trash and miss out on a lot. Coffee grounds can be used to combat pests such as fungus gnats or as a compost additive.
Properties of coffee grounds
Coffee grounds have many different ingredients that we can use. In addition to nitrogen, phosphorus and potassium, it also contains tannic acids, antioxidants and traces of caffeine. Basically, an average of 2% nitrogen, 0.4% phosphorus and 0.8% potassium remain in the coffee filter.
The slightly acidic pH of coffee grounds is ideal for citrus plants [Photo: blue caterpillar / Shutterstock.com]
Since the coffee grounds are slightly acidic (its pH value is around 6.5), it is particularly suitable for plants that prefer acidic soils. These include, for example, citrus plants. You can find out more about fertilizing citrus plants such as lemon trees here.
Benefits of using coffee grounds as a fertilizer
Of course, one of the greatest advantages of coffee grounds as a fertilizer is that it occurs almost by itself in every household and does not have to be bought separately. This saves you the trip to the hardware store and in this way you can reuse a waste product. Coffee grounds are also attractive to earthworms. This is a great advantage, because earthworms loosen the soil and create a crumbly structure of the soil. They also help break down organic matter in the soil.
However, coffee grounds have a repellent effect on pests such as snails or ants. These little pests can’t stand the smell of coffee and caffeine and will therefore avoid the areas that are fertilized with it.
So the benefits of using coffee grounds as a fertilizer are as follows:
Occurs in the household
Is (in principle) free
Slightly acidic pH
Repulsive to snails and ants
For which plants is coffee grounds suitable as a fertilizer?
When using coffee grounds as fertilizer, it is particularly important to ensure that it does not become moldy. So dry the coffee grounds thoroughly. There is a particular risk of mold in fully automatic coffee machines, where the coffee grounds are collected in a container for a long time. But no matter what kind of coffee machine you have, always dry the coffee grounds before using them as fertilizer to reduce the risk of mold. To do this, simply spread the damp coffee grounds flat – for example on a baking sheet – and let them dry there.
Before using it as a fertilizer, the coffee grounds should be dried thoroughly [Photo: Monthira / Shutterstock.com]
To use it, you should not only sprinkle the dried coffee grounds over the earth, but rather work it into the earth. This allows it to be broken down better and release the nutrients where they are needed. You shouldn’t overdo it with a coffee grounds fertilizer.
Fertilize garden plants with coffee grounds
You can fertilize with coffee grounds up to four times a year outdoors. Over-fertilization with coffee grounds is practically impossible. The best thing to do is to work the substance a little bit into the soil. You can also simply mix the dried coffee grounds with potting soil and place your plants in this soil. All you have to do is mix the contents of a coffee filter (about 30 g of coffee grounds) with the potting soil in a 10 liter sack. This way the earth doesn’t become too acidic. You can also simply add the coffee grounds to the compost and let it rot there. There it has a positive effect on composting and also provides nutrients. This method is extremely effective because the coffee grounds attract earthworms, which help with composting. This way you get an optimal organic fertilizer.
When it comes to dosing, it is of course an advantage if you try it yourself and start with small amounts at the beginning. The needs of the plants and their sensitivity are often very different.
Fertilize indoor plants with coffee grounds
With house plants, it is sufficient to fertilize them once in winter and once in spring. One to two full teaspoons per plant are sufficient for this, which corresponds to about 4 to 8 g of coffee grounds per plant. Be careful, however, because this dose will lower the pH value in the pot and some of our indoor plants could resent this. Don’t forget to repot your houseplants regularly afterwards and provide them with fresh substrate.
You can also fertilize indoor plants with coffee grounds [Photo: Monthira / Shutterstock.com]
You can still mix the coffee grounds or leftover coffee with water and water your houseplants with it. To do this, for example, mix old coffee and the irrigation water in a ratio of 1: 1 and use it to water your plants. Be careful not to water the leaves, but simply all around the plant base. You can do the watering and fertilizing in one step.
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Coffee grounds as flower fertilizer
When speaking of flowers, annual summer flowers are usually meant. These bloom profusely and usually have a high need for nutrients. Because coffee grounds contain only small amounts of nutrients, fertilizing the flowers with it is not harmful, but it is by no means sufficient. The large amount of organic material and the tannic acids it contains also inhibit the rapid release of the nutrients it contains. Our hungry summer flowers could even slide into malnutrition if the coffee grounds were given too generously.
Nevertheless, the beauties can benefit from the coffee grounds: Together with a strong flower fertilizer – such as our Plantura organic flower fertilizer – soil organisms convert the hard-to-digest coffee grounds. This can produce valuable humus. This improves the soil properties, which is very useful for the often spoiled summer flowers. To do this, mix coffee grounds and flower fertilizer in a ratio of 3: 1. A good alternative to this process is to compost the coffee grounds along with more nutrient-rich waste. You can then use the compost to fertilize your summer flowers.
After fertilizing with coffee grounds, the orchid needs to be watered well [Photo: Stanislav71 / Shutterstock.com]
Plantura organic flower fertilizer
Coffee grounds as fertilizer for orchids
The beautiful orchids (Orchidaceae) also benefit from coffee grounds as fertilizer – but only if they are planted in orchid substrate. Unfortunately, if your orchids are grown in hydroponics, fertilizing with coffee grounds is not possible. The coffee grounds are very easy to use with orchids: you distribute the coffee grounds on the surface and then simply water the orchids. Another possibility is to mix some coffee grounds with the earth. Be careful not to use too much coffee grounds, however, as orchids are extremely delicate houseplants. Here you should try it out first and see what happens. Just add a small amount of coffee grounds to the orchids and keep an eye on the plant. If the plant finally changes negatively, then you better stay away from this fertilizer for your orchids. You can find out more about the correct care of orchids here.
Coffee grounds as fertilizer for roses
Roses (pink) delight our eyes with their wonderful flowers. But the queen of flowers needs a lot of nutrients, after all, she is one of the heavy eaters. To give your roses a burst of energy, you can spread about half a cup of coffee grounds around your roses once a month and work them lightly into the soil. You can do this until the end of June, after which roses should not be fertilized. You can safely use coffee grounds as an alternative or as a supplement to your usual rose fertilization and then enjoy the great effect. However, there are usually too few nutrients in the coffee grounds to only fertilize your roses with them.
Coffee grounds as fertilizer for hydrangeas
Hydrangeas should ideally be bushy and abundant in bloom. But this only works if they are properly supplied with nutrients. After all, they place high demands on the floor. Therefore, coffee grounds are ideal as a supplementary fertilizer for hydrangeas, because they prefer acidic soil – coffee grounds are slightly acidic.
The slightly acidic coffee grounds are ideal for fertilizing hydrangeas [Photo: Mariola Anna S / Shutterstock.com]
It also contains many minerals and optimally supports the hydrangeas in their growth. Coffee grounds alone are not enough to fertilize hydrangeas because the nutrient levels are ultimately too low for that. However, it is an ideal complement to your conventional hydrangea fertilization. Don’t just spread the coffee grounds around the hydrangeas on the ground, but work them into the soil so that they can develop their full effect. A thick layer of coffee grounds can quickly form a water-impermeable layer on the surface, which of course is not desirable. If you want to learn more about fertilizing and caring for hydrangeas, you can find more information in our special article.
Coffee grounds as fertilizer for tomatoes
Tomatoes (Solanum lycopersicum) can also be fertilized with coffee grounds. However, they are very draining vegetables and therefore need a lot of nutrients. Coffee grounds are certainly an effective fertilizer for tomatoes, but unfortunately not enough. You should therefore only use the coffee grounds in addition to an optimal tomato fertilizer. Our Plantura organic tomato fertilizer, for example, is perfect for this. This supplies your tomato plants with the necessary nutrients and consists of purely vegetable components. For tomatoes in pots, however, the liquid Plantura organic tomato & vegetable fertilizer is more suitable, as the incorporation of a granular fertilizer would put the plants under stress.
Plantura organic tomato fertilizer
Coffee grounds as an organic fertilizer supplement
Coffee grounds contain important nutrients and are an optimal fertilizer supplement to provide your plants with nutrients. However, the content of nutrients in coffee grounds is too low to be able to fertilize with coffee grounds alone. Another possibility is the use of coffee grounds as a supplement to another fertilizer – such as our Plantura organic fertilizer. This gives you an optimal, well-rounded supply of nutrients in your garden.
Fertilizing with coffee grounds is a popular home remedy. We’ll show you why coffee grounds are good for your flowers and how to use coffee grounds fertilizer.