Every coffee drinker consumes an average of seven kilograms of coffee beans and powder per year, which are often disposed of directly in household waste after brewing.
But that doesn’t have to be the case: Coffee grounds can not only be composted but are also ideal as a natural fertilizer for plants.
Coffee grounds contain many important plant nutrients: nitrogen, phosphorus, sulfur, and potassium.
Use only dried coffee grounds so that the root ball does not become moldy.
Indoor plants are best fertilized with water diluted coffee grounds.
1. Fertilizing With Coffee Grounds: Plant Nutrients In The coffee Powder
Brewing coffee powder – filter coffee, for example – produces a large number of coffee grounds that can be used as a natural fertilizer. Coffee pods can also be taken apart, giving them a second raison d’être.
You can use these coffee grounds as garden fertilizer or sprinkle them on your balcony and indoor plants. The purely vegetable source product is considered very rich in nutrients and can improve soil quality:
- Coffee beans contain plant nutrients such as potassium, sulfur, nitrogen, and phosphorus (macronutrients), which are not destroyed during roasting or are only flushed out in small quantities during boiling.
- Roasting the coffee beans produces humic acids, which give the coffee a slightly acidic pH.
- Fertilizing with coffee powder enriches the soil with hummus.
Since there is less waste and you often no longer need any other (chemical) fertilizer thanks to the many nutrients it contains, the use of coffee grounds as fertilizer is considered particularly sustainable.
Earthworms also like coffee and are attracted to it. The invertebrates are considered very useful because they improve soil quality.
Coffee grounds provide flowering and useful plants with important nutrients and trace elements. To ensure that these flush out optimally and that the powder does not become moldy due to the moisture, you should first observe a few things:
- Collect the coffee grounds in an airy and dry place. For example, hang a fine mesh sieve in a bucket so that the wet powder can dry completely.
- Spread the dry coffee grounds over the root area to fertilize.
- Then lightly work the coffee grounds into the soil or cover the surface with some mulch. Fertilizer left just on the surface decomposes too slowly to be truly effective.
- If you want to add coffee grounds fertilizer to your potted plants, you can incorporate it when you report them. Mix some dry coffee grounds with the new potting soil.
Coffee grounds as a pesticide
In addition to fertilizer, coffee powder is also considered a possible pesticide that can keep pests away. Studies have shown that the caffeine it contains can have a lethal effect on predators such as slugs.
However, caffeine is considered a poison that can kill not only unwanted pests but also beneficial insects. That’s why they use of coffee powder as a pesticide is only conditionally recommended.
However, a small dose of cold coffee or coffee powder can be used to control fungus gnats: The caffeine destroys the larvae that are still in the soil.
Aphid infestations can also be reduced if you apply a little coffee to the leaves of the plant, for example with a spray bottle.
Since coffee grounds cover up many odor traces, you can also use them on an ant infestation.
2. What Plants Can I fertilize With Coffee Grounds?
The coffee grounds fertilizer is particularly suitable for plants that prefer humus-rich soil. However, coffee also has a soil acidifying effect, which does not benefit all plants – the fertilizer can even harm acid-intolerant plants.
Therefore, find out before use whether a plant may be fertilized with coffee grounds.
Type of Plants You Can Fertilize With Coffee Grounds?
- Garden plants: Coffee grounds are a good fertilizer for many garden plants that grow in beds or plant pots. For example, hydrangeas, rhododendrons, or blueberries can easily be supplied with natural fertilizer once a week.
- Houseplants: Coffee grounds as fertilizer for houseplants are only recommended to a limited extent: they decompose very slowly on the pot ball and often start to mold. For this reason, use only very few coffee grounds for potted plants that stand indoors – such as herbs – and work them lightly into the upper layer of soil. It is better to fertilize the houseplants not with the powder, but with cold black coffee:
- Mix the coffee with water in a ratio of 1:1.
- Use the mixture very sparingly, otherwise, there is a risk of over-fertilization of the houseplants (= over-acidification of the pot bale).
- We recommend No more than half a cup of diluted coffee per plant.
These plants you should not fertilize with coffee grounds:
Gooseberries, apple trees, tulips, spring bulbs, onions, blackberry bushes, boxwood, chrysanthemums, clematis, strawberries, gladioli, bluebells, crocuses, lavender bushes, daffodils, parsley, salsify, celery.
You can quickly recognize that your plant does not tolerate fertilizing with coffee grounds: Overfertilized plants show clear leaf damage, growth inhibition, or stunted growth.
During the winter dormancy, you should refrain from fertilizing the houseplants.
3. Indirect Fertilizing: Composting Coffee Powder
Instead of applying the coffee grounds directly to the plant, you can also use them indirectly as fertilizer by composting them.
In this way, the old coffee grounds can be processed together with green waste and eggshells to form humus, which you can then in turn use for fertilizing.
Classic paper filter bags also do not belong in the household waste but can be composted.
However, to prevent the filter from becoming moldy, you should empty the coffee grounds.