Use coffee grounds as fertilizer
Coffee grounds usually end up in household waste or in the compost. However, it can also be used directly as a fertilizer for garden plants.
Coffee grounds are often underestimated as a natural fertilizer because they contain a comparatively high amount of nitrogen for a purely plant-based product. The nitrogen, sulfur and phosphorus-rich protein content of raw coffee beans is an impressive eleven percent. The roasting process completely decomposes the vegetable protein, as it is not heat-stable, but the above-mentioned plant nutrients are largely retained in the breakdown products. During the subsequent brewing, only a small proportion of the plant nutrients are flushed out. In addition, humic acids are formed during roasting - this is why the coffee grounds, in contrast to freshly harvested coffee beans, have a slightly acidic pH value.
Coffee grounds are best for fertilizing plants that love acidic, humus-rich soil. These include, for example, hydrangeas, rhododendrons and blueberries. The coffee grounds are spread flat into the ground or covered with a little mulch. Cold coffee diluted with water can be used for indoor plants.
If you want to use your coffee grounds as fertilizer, you should collect them first, because it is hardly worth going into the garden with a single used filter bag and sprinkling the contents around the plants. Instead, collect the coffee grounds in a bucket in an airy, dry place. It is best to hang a fine-mesh sieve in it so that the fresh coffee grounds can dry quickly so that they do not start to go moldy.
When you have collected a large amount, sprinkle a few handfuls of the dry powder around the root area of each plant. Coffee grounds have a slightly acidic effect on the soil and also enrich the soil with humus. Coffee grounds are best for fertilizing plants that love acidic, humus-rich soil. These include Hydrangeas, Rhododendron und Blue berries. Important: Spread the coffee grounds flat into the ground or cover it with a little mulch - if it just remains on the surface of the ground, it decomposes very slowly and it is hardly effective in fertilizing.
Tip: With Balcony flowers and other potted plants, you can mix a few handfuls of coffee grounds into the new potting soil before repotting, in order to enrich them with further nutrients and trace elements.
You can also use your coffee grounds indirectly as fertilizer for the garden by first composting them. Simply sprinkle the damp powder on the surface of your compost heap. You can compost the filter bag with it, but you should pour out the coffee grounds beforehand - otherwise it will start to mold easily.
Coffee grounds should not be used as fertilizer for house plants, because the powder hardly decomposes on the root ball and sooner or later starts to go moldy. However, cold black coffee from the pot is a free fertilizer. Simply dilute it with water in a ratio of 1: 1 and use it to water your indoor plants, container plants and balcony flowers. It should be used very sparingly, especially with house plants - do not use more than half a cup of diluted coffee per plant and week, otherwise there is a risk that the pot ball will acidify too much and the house plants will no longer grow properly.
A few years ago, Nature magazine reported that a two percent caffeine solution was successfully used in Hawaii to combat snails. After the first wave of euphoria subsided, hobby gardeners quickly became disillusioned: You need almost 200 grams of powder to make a cup of the highly concentrated anti-snail coffee - an expensive pleasure. In addition, although caffeine is an organic pesticide, it is still a highly toxic one. In such a high concentration it is likely to kill numerous other living things.
A normal strong coffee diluted 1: 1 with water works well against dark-winged fungus gnats on houseplants, because caffeine is poisonous for the larvae living in the pot ball. You can also spray the coffee solution with an atomizer to combat aphids.