An average home generates a large amount of coffee grounds that we automatically throw away. However, this is not the only way to get rid of them.
Coffee grounds are an excellent plant food because they contain important nutrients such as nitrogen and potassium. These nutrients help plants grow healthy and strong. Additionally, coffee grounds can also help maintain soil pH, which means it can be helpful for plants that need a more acidic environment to grow.
Which plants can be fertilized with coffee grounds?
All plants can benefit from coffee grounds without any distinction, as long as they mix well with the substrate and are not the only source of soil for pots. This grounds are already washed off from the preparation of the coffee, so its mineral content is not very high, but it can enrich the substrate with certain nutrients, vitamins and, above all, organic matter.
This is very interesting from a biological point of view, because even if we think that a pot can be an inert environment, this small part of the substrate will harbor billions of bacteria, yeasts, fungi and other micro-organisms which act in synergy with plant roots.
An even more comfortable solution is to take advantage of the coffee grounds by introducing them directly into the bag of substrate or compost, since they will mix better and you will not have to constantly add them to the pots.
Of course, although we have mentioned potted plants several times, coffee grounds are perfectly valid for any outdoor plant, grown in the garden, that can create a mulch or a surface layer with these grounds to enrich the substrate. Maybe the coffee grounds generated from a house isn’t enough to make it representative in a garden, but think of any bar near you and the huge amounts of coffee that can be generated.
Benefits of using coffee grounds for your plants
Rich source of organic matter
Maintaining a high level of organic matter in the soil or growing medium is essential to maintaining healthy and productive plants. A soil is considered fertile from 2% organic matter, but if we are talking about substrates for pots, this content must be significantly higher.
Coffee grounds are an enriched source of organic carbon and readily available and free organic matter for roots and microbiology. Use the soil continuously to enrich the properties of the substrate or mix it directly into the soil to create your own compost with an acid pH.
Contains soluble salts as a source for plants
Although coffee grounds contain salts diluted by the coffee brewing process, they are a free source of certain minerals that we cannot obtain from water and only through fertilizers.
The main contributions of coffee are calcium (146 mg), phosphorus (192 mg), magnesium (201 mg), potassium (1653 mg) and essential micronutrients such as zinc (0.71 mg), copper ( 1.7 mg) or iron (17 mg). However, the concentration will be much lower (2 to 3 times minimum).
In terms of vitamins, the main source of intake is the group of vitamins B, K and E.
In general, the mineral source of coffee grounds is insufficient to replace the organic or mineral fertilizer that we can bring to our plants, but it is a complementary and very interesting source due to its high organic matter content.
Source of simple sugars
There are different types of sugars in nature, all of organic origin, which act as complexing agents (protectors) of metals such as microelements, calcium or potassium. Many, in turn, have a biostimulating effect on plants, increasing the uptake of nutrients by leaves and roots.
Finally, these sugars contained in coffee grounds are prebiotics that promote microbial life and biologically enrich the substrate.
Source: SpruceProblems with coffee grounds
Coffee grounds can be an excellent fertilizer for many plants. Indeed, the soils are rich in nitrogen, magnesium and calcium, among other minerals essential to the good growth of your plants. However, using coffee grounds as compost poses certain problems.
Coffee grounds are very acidic
This means that if the amounts are not controlled properly, they can be harmful to the soil and the roots of your plants. But let’s contextualize it with numbers. The pH of coffee is generally around 5, although some light roasts move to values around 4.7. Therefore, coffee is acidic. If you use it directly as a substrate, without mixing it with anything, very few acid-loving plants will grow optimally. However, if you mix it with universal substrates, sand, coconut fiber or any other element with a neutral or basic pH, it will be a perfect mix.
It can generate fungus (not harmful)
Any organic source, such as coffee, is likely to generate molds and yeastsespecially when they are wet. Although these fungi are not really a problem for the plant and they do not cause any type of disease (they only feed on decaying organic matter), it is not very attractive to see them in the pots of your house. An easy and simple way to avoid its presence is to mix the coffee grounds well with the substrate. To do this, you can use a small garden shovel or a simple spoon to mix well with the substrate without damaging the roots.
Coffee grounds contain salts
These calcium, magnesium, potassium and sodium salts make good fertilizer in small amounts, but too much salt can damage and cause problems for your plants. Therefore, it is important that the grounds mixes with other substrates before using them in your garden or pots. In addition, it is important to know that the floors have been washed beforehand, to remove most of the salts.
Additional Note: Caffeine does not affect plants.
If caffeine has a neuro-activating effect on animals, this is not the case for plants. It was thought that caffeine, having a chemical structure similar to cytokinins, could have a positive physiological action for plants. However, recent studies conducted by the University of Almería did not find statistically significant differences in the production of horticultural crops in greenhouses, so it is suggested that caffeine does not exert any positive or negative action on crops.