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Which Houseplants Can Be Fertilized with Coffee Grounds

Fertilize houseplants with coffee grounds
Is it worth fertilizing houseplants with coffee grounds? Photo: Getty Images / ThamKC

January 16, 2025, 4:26 pm | Read time: 5 minutes

Coffee grounds are considered a good source of nutrients for some plants in the garden. But what about houseplants? myHOMEBOOK gives tips on how to deal with the leftovers from drinking coffee and houseplants.

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Germans drink just under four cups of coffee per person per day. This was the result of a survey conducted by the German Coffee Association in 2022. As coffee consumption has continued to rise in recent years, this figure could now be even higher. Anyone who doesn’t use capsules and throws away coffee grounds every day is right to ask themselves: Couldn’t I use the brewed coffee grounds for something else? The answer is clearly yes – because coffee grounds can also be used to fertilize houseplants.

Fertilizing Houseplants with Coffee Grounds

Instead of simply disposing of the filter or knock box (or coffee grounds bin) with coffee grounds in the organic waste, houseplant keepers can do something good for their plants. As a fertilizer, the already-brewed coffee provides many plants with plenty of new nutrients in the substrate. Coffee grounds have the following advantages as a fertilizer for houseplants:

  • Nutrients: Coffee grounds contain important nutrients such as nitrogen, potassium, and phosphorus, which can promote plant growth. These nutrients are released slowly, which is particularly beneficial for plants with continuous requirements. The coffee grounds, therefore, act as a kind of long-term fertilizer.
  • Soil improvement: Coffee grounds can improve the soil structure by promoting aeration and water absorption. Microorganisms decompose the coffee grounds, which improves the soil quality.
  • pH value: Fresh coffee grounds are slightly acidic. Plants that prefer acidic soils benefit from the acidic environment. These include ferns, azaleas, and orchids.
  • Pest repellent: Coffee grounds can deter pests such as fungus gnats. If you often have to deal with fungus gnats, you can use the remains of your morning coffee as a prophylactic measure against the insects without using chemicals.
Zimmerpflanzen mit Kaffeesatz düngen
Coffee grounds don’t necessarily have to be thrown away. As a fertilizer, they help some plants with their nutrient supply.

Why Coffee Grounds Are Not Always Suitable for Indoor Plants

  • Mold growth: Coffee grounds can quickly become moldy if they are permanently damp. This not only looks unattractive but can also affect the health of the plant.
  • Over-fertilization: Too many coffee grounds can lead to oversaturation of the soil and, thus, damage the roots. Anyone who has fertilized the surface of a houseplant with coffee grounds should wait a few weeks before the next application. It takes time for the nutrients to be washed out of the coffee grounds.
  • Caffeine residues: Some plants react sensitively to caffeine, which can remain in small quantities in the coffee grounds.
  • Unsuitable pH value: Not all plants like acidic soils. Coffee grounds can be problematic for plants that prefer neutral or slightly alkaline soils. These include, for example:
    • Sansevieria (snake plant): This robust plant prefers well-drained soil with a neutral pH value. Coffee grounds can make the soil too acidic.
    • Palm species (e.g., Kentia palm, Areca palm, or Yucca palm): Many palm trees prefer neutral to slightly alkaline soil. Acidic soils can inhibit growth.
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Using Coffee Grounds Correctly as a Fertilizer for Houseplants

Even though coffee grounds are a sustainable and inexpensive alternative to other types of fertilizer, there are a few things to bear in mind when using them for houseplants. For example, coffee grounds should always be completely dry before they are spread on the substrate of the houseplants. The best way to do this is to spread them out thinly on a tray and leave them to dry for a few days in a warm and well-ventilated room.

In addition, the amount of coffee grounds used should be so small that there is only a thin layer of coffee powder on the substrate. Otherwise, the pH value could be too acidic for the fertilized plant.

If you want to be even more careful, mix the dried coffee grounds with potting soil suitable for the plant in question and apply the mixture as a thin top layer to the root ball of the houseplant.

This article is a machine translation of the original German version of MYHOMEBOOK and has been reviewed for accuracy and quality by a native speaker. For feedback, please contact us at info@myhomebook.de.

Topics Fertilizer Home remedies Houseplants
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