Coffee grounds were already used in grandmother's time to loosen up the structure of potting soil and to fertilize the plants. Today more is known about the properties of the supposed waste product. As supplementary fertilization, it is suitable for most plants.

Coffee is an excellent fertilizer for many plants

Table of Contents

Show all
  1. the essentials in brief
  2. For which plants?
  3. use coffee grounds
  4. ingredients and effects
  5. Application examples
  6. frequently asked Questions

    7. the essentials in brief

    • Coffee grounds are suitable for all plants that tolerate a pH between 6.0 and 7.0. These include vegetable plants, ornamental shrubs and flowering plants. Eria plants, lightly consuming flowering plants or herbs from poor locations do not tolerate coffee grounds.
    • The powder is dried before use. Optimal results are obtained when the powder is worked into the soil.
    • Coffee grounds have a slightly acidic to neutral pH and contain mainly nitrogen and other nutrients such as potassium and phosphorus. In order for plants to be able to use the nutrients, the activity of microorganisms is necessary.
    • It can be used for citrus plants or the lawn, for mulching and for mushroom cultivation.

    Which plants like coffee grounds as fertilizer?

    Coffee is just the thing for tomatoes and other plants that prefer moderately acidic soil

    Coffee grounds are a good fertilizer for plants that grow in a moderately acidic to almost neutral environment. You can use the free fertilizer in the vegetable patch, or work it into the substrate under hedges and shrubs. Some houseplants can be supplied with an aqueous extract from the coffee grounds. Seedlings do not tolerate coffee fertilization well, as they tend to shoot quickly due to the excessive supply of nitrogen.

    preferred pH Examples: good NPK fertilizers Coffee grounds suitable?
    orchids 5.5 to 6.0 10-8-10 yes, if plants grow in substrate
    roses 5.5 to 7.0 7-5-8 Yes
    hydrangeas 4.0 to 5.5 (up to 6.0) 7-3-6 conditionally, as a supplement
    tomatoes 6.5 to 7.0 7-3-10 yes, as a supplement
    paprika 6.2 to 7.0 6-6-8 yes, as a supplement
    geraniums 5.5 to 6.0 3-7-10 conditional, very economical use
    cucumbers 5.6 to 6.5 4-5-8 Yes
    blueberries 4.0 to 5.0 3-3-5 conditional, economical use
    lemon Tree 5.5 to 6.5 14-7-14 yes, as a long-term fertilizer

    Since the nutrient requirements of a plant change over the course of the growing season, fertilizers with different NPK ratios are necessary depending on the season. Nitrogen-rich fertilizers such as coffee grounds are particularly useful for many plants in the spring, as they promote the growth of leaves and shoots.

    Can coffee grounds be used without restriction?

    Coffee grounds are less acidic than you think

    There is a widespread myth that coffee grounds should only be used for plants growing in acidic soil. In fact, the pH of the coffee residues is not particularly acidic and can lead to deficiencies in real ericaceous plants such as rhododendrons. The plant likes levels around 4.5 and tends to have leaf veins turning dark green if the pH is too high. Plants that depend on calcareous soil tolerate small amounts of coffee grounds. This includes zucchini, which thrives at a neutral pH of 7.0.

    Coffee grounds usually have a very slightly acidic pH value and are not suitable for ericaceous plants.

    Coffee grounds for flowers

    Whether flowers should be provided with the natural fertilizer depends on the species. As with vegetable plants, there are flowers that consume less and others that thrive better in poor locations. In general, flowering plants should be fertilized sparingly with coffee grounds, as the NPK ratio is not optimal. These plants do better when given less nitrogen and more phosphorus. These plants include bluebells, boxwood, carnations, and bulbous plants such as daffodils and tulips.

    Summer flowers benefit from coffee grounds:

    • have a high nutrient requirement, so that coffee grounds are not sufficient as fertilizer
    • It is better to mix and administer three parts of coffee grounds and one part of flower fertilizer (€1.95).
    • Soil organisms convert coffee grounds faster and produce humus
    • improved soil properties support the growth of summer flowers

    herbs

    Most herbs are undemanding and thrive without additional fertilization. However, herbs in partially shaded locations have different needs than sun-loving plants. Mediterranean herbs are dependent on poor soil and can become diseased or die if there is an oversupply of nutrients. Other kitchen herbs are nutrient-depleting and attach more importance to additional fertilization.

    Garden and potted herbs are so different:

    • Herbs from poor soils: lavender, rosemary or savory do not tolerate coffee grounds
    • Lime-loving herbs: Coffee fertilizer is unsuitable for oregano, sage or borage
    • nutrient-sapping herbs: lemon verbena or chives may be fertilized with coffee

    use coffee grounds

    The basic requirement for fertilizing with coffee grounds is preparatory storage. If you use it wet, mold will quickly form. The powder does not go bad if it becomes moldy. However, it must then be sterilized before use so that the mold does not spread in the soil.

    dry

    Fill the residue from the coffee filter into a wide container in which you can spread the material loosely. The base of a mini greenhouse is ideal for drying. Place the jar on a sunny windowsill and mix the powder daily. You can break up lumps with a fork.

    Another option is drying at 50 to 100 degrees Celsius in the oven. After about 30 minutes the substrate is dry. You can also spread coffee grounds out on a plate and microwave them on medium power for five minutes.

    Use

    If you put young plants in the garden, you can put a few teaspoons of coffee grounds in the planting hole. Provide your potted plants with a mixture of potting soil and coffee grounds in small quantities when repotting. For plants in coarse substrate, watering with an aqueous extract of coffee grounds is recommended.

    To do this, add the finely crumbly powder to water and let the mixture steep for a few days. Be careful not to collect too much coffee powder on the substrate surface. If that's the case, consider working it into the soil with a small rake.

    • Lance fertilizer: sprinkle coffee grounds on the bed once or twice a year
    • instant fertilizer: if necessary, brew coffee grounds again and pour when cooled
    • composting: Coffee grounds should not make up more than 20 percent of the compost volume

    How often and how much coffee grounds?

    As for the dosage, you should experiment for yourself. Depending on the type of coffee, the ingredients can vary and the fertilizing effect differs with regard to your plants and the environmental conditions. Start with small amounts and see how your plants respond. You can then slowly increase the dose until you are in an optimal state.

    Guidelines for orientation:

    • Coffee grounds can be used outdoors four times a year
    • Work the contents of a coffee filter (about 30 grams) into the substrate for each fertilization
    • Fertilize indoor plants with coffee powder in winter and spring
    • two teaspoons (about four to eight grams) of powder per plant is sufficient

    Ingredients and effects in the garden

    The fact that coffee grounds are valuable for rhododendrons, peonies and ferns is primarily due to the ingredients and less to the pH value. This is subject to fluctuations, which are influenced by coffee powder but not permanently sealed. In order for the plants to benefit from the valuable ingredients, you must incorporate the residues into the soil.

    ingredients

    Coffee is rich in nitrogen, phosphorus and potassium

    Coffee grounds contain numerous nutrients, trace elements and tannic acids as well as traces of caffeine and bioactive substances such as antioxidants. This applies primarily to the residues in the coffee filter. More than ten percent of coffee grounds are made up of nitrogen-rich proteins. The average NPK ratio is 2-0.4-0.8. When it is prepared in the espresso pot, most of the ingredients go into the coffee.

    Effect of coffee grounds:

    • nitrogen: stimulates leaf growth
    • phosphorus: promotes flowering and fruit ripening
    • potassium: supports cell structure and gives the plant stability

    Coffee grounds is an organic fertilizer with a NPK ratio that is beneficial for many plants. Due to the nitrogen-rich nutrient composition, the residue left in the coffee filter is ideal as an additional fertilizer. It provides a good complement to compost, which often has low levels of nitrogen, and is a perfect alternative to commercial fertilizers.

    changes in pH

    Coffee grounds usually have a pH between 6.4 and 6.8 and are therefore in the slightly acidic to almost neutral range. This makes it an unproblematic fertilizer for most plants. Researchers at Washington State University have found that pH varies greatly depending on the strain. According to their results, there are varieties with values between 4.6 and 5.26 and those with values of 7.7 or 8.4 tend towards the alkaline environment.

    The scientists could not confirm that the soil becomes acidic after prolonged use of coffee grounds. The experiments showed that the pH value of the substrate treated with coffee grounds increased in the first two to three weeks and then gradually decreased. This indicates that the value fluctuates in the course of microbial activity and does not remain constant over time.

    tips

    Pay attention to the acidity of the coffee. From this it can already be deduced in which environment the residues are in the filter. Mix coffee grounds and egg shells, which you grind finely beforehand. The shells are calcareous.

    This is how plants benefit from nutrients

    According to garden experts, coffee grounds as the top layer of substrate for potted plants have no or a very delayed effect. This is because the powdered substance offers no plant-available nutrients. These are bound in the fine particles and must first be released by microorganisms in the soil.

    It is therefore important that you incorporate coffee grounds into the soil. The best fertilizing results are achieved when used in the garden. Here, coffee grounds are used to build up the soil, because humus-forming substances are produced as part of the decomposition.

    • Bacteria and fungi break down chemical components in coffee grounds
    • Earthworms pull coffee particles into the soil, improving structure
    • when the coffee powder is broken down, humic substances are formed

    background

    Why fresh coffee grounds are not fertilizing

    The C/N ratio represents the proportions by weight of carbon (C) and nitrogen (N) found in soil. It is given as a number and serves as an important indicator of the availability of nitrogen to plants.

    The smaller the number, the tighter the carbon-nitrogen ratio and the more nitrogen available to plants. Fresh coffee grounds have a suboptimal ratio, because the values are very high and vary between 25 and 26. That is why fresh coffee grounds that are scattered on the ground do not bring any noticeable success.

    The plants cannot take up the available nitrogen in the soil. Over the course of a year, the coffee powder is decomposed by microorganisms and the C/N ratio changes. It drops to 21, 13 and further to 11 or even 9, so it takes a year for the plants to benefit from directly applied coffee grounds. In this respect, it behaves like fresh grass cuttings.

    Application examples

    Over-fertilization in the garden is unlikely

    If you use coffee grounds correctly, you can use them in many ways in the garden. Over-fertilization is almost impossible. Rather, the plants suffer from suboptimal soil structures or an unfavorable water-air balance if you give too much coffee powder.

    Coffee grounds look so different:

    • Sugar beet seeds germinate better
    • better growth in cabbage and soybean plants
    • Seed growth of alfalfa, white and red clover is inhibited
    • Geraniums, fern asparagus and spiderwort show stunted growth

    lawn

    Many grasses prefer a slightly acidic environment with a pH of 5.5. Fertilizing with coffee grounds can improve the growth of your lawn. Spread the dried powder evenly over the area and work it into the turf. Subsequent irrigation ensures that the particles are washed into soil pores.

    This allows microorganisms to do their job and decompose the material. Alternatively, watering with a diluted coffee solution is recommended. Freshly brewed coffee is mixed with water in a ratio of 1:5 and then distributed with the watering can.

    tips

    Check beforehand which species are in your lawn. Not all grasses tolerate coffee grounds. The Italian ryegrass often grows in park lawns and shows growth disorders when fertilized regularly with coffee grounds.

    citrus plants

    The Mediterranean plants get a basic fertilizer with a long-term effect at the end of April in order to benefit during the entire growth period. Citrus plants mainly need nitrogen. Phosphate is important for flower and fruit development. However, all citrus species are sensitive to phosphorus fertilizers.

    It is ideal when the concentrations of nitrogen and potassium are about the same and the phosphate content is lower. Coffee grounds are not suitable as the sole fertilizer, but should be administered as a long-term fertilizer. It promotes lush growth and ensures lush green leaves.

    A coordinated fertilization:

    • only fertilize during the growth phase between April and September
    • Small trees in bright and warm locations have a higher nutrient requirement
    • Only moderately fertilize potted plants in shady and cool locations

    compost

    Coffee is also a boon for the compost

    Over the course of several months, special bacteria and fungi that live in the compost break down all of the chemical components in the coffee grounds. Earthworms use the fine particles as a food source. Make sure that the starting material is as diverse as possible in order to promote a large number of microorganisms.

    Ideally, compost should contain no more than 10 to 20 percent coffee grounds. Concentrations greater than 30 percent can negatively impact macro habitat. However, you do not have to worry that an acidic compost will develop. The pH value fluctuates constantly due to the activity of the microorganisms.

    mulching

    Coffee grounds consist of fine particles and have a crumbly structure when dry. When it soaks up moisture, it tends to compact easily. In this form, coffee grounds form a barrier to moisture and insulate the floor from air circulation. When using coffee grounds for mulching, you should only apply the powder in thin layers and no more than an inch thick. Cover this layer with coarse organic materials such as wood chips.

    Fresh coffee grounds are unsuitable:

    • Soil can't breathe
    • aerobic microorganisms do not get oxygen
    • Mold growth is encouraged

    mushroom growing

    Edible mushrooms can be grown in a flower pot filled with coffee grounds. The substrate should not be older than two to three days, as mold spores will settle on the surface if it is stored for a long time. Small amounts of coffee grounds are enough for the added mushroom mycelium to fully spread in the fresh substrate. This growth phase lasts about 14 to 28 days.

    youtube

    frequently asked Questions

    What is in the coffee grounds?

    Coffee grounds contain numerous substances that do not get into the coffee when it is brewed. Included in the residues are various antioxidants such as caffeine, chlorogenic acids, and the nitrogenous and yellowish-brown melanoidins.

    The powder is rich in tannic acids and nitrogen-rich proteins. Non-water-soluble polysaccharides, which form the cell walls of the coffee bean, are also preserved.

    In addition to the nutrients nitrogen, phosphorus and potassium, which are important for the plants, the coffee grounds contain essential oils that are responsible for the typical aroma. These have antioxidant and antimicrobial properties and act as a deterrent to plant pests.

    Can Coffee Grounds Lower Soil pH?

    Linda Chalker-Scott of Washington State University has researched that adding coffee grounds to potting soil does not result in a drop in acidic pH. Rather, the value increases over time. Researchers suspect that this increase is caused by microbial activity. Only after the organisms have broken down the material does the pH drop.

    Can I compost coffee grounds without restrictions?

    There is still no scientifically proven information on how much coffee grounds a compost heap can take. The more varied the starting material, the better your compost will work. Basically, ten to 20 percent coffee powder is not harmful to your compost. The coffee residues contain carbohydrates that are broken down and broken down by the microorganisms.

    How else can coffee grounds be used?

    Encafé is a flower pot made from coffee grounds and natural wax. It serves as a plant pot that is placed in the ground with the plant. Here it decomposes and acts as a natural fertilizer. The aromatic substances protect the plant roots from infestation by pests such as nematodes.

Category:

Care tips