Coffee Grounds And Wood Ash: Are They Suitable Fertilizers?

Last updated on October 23rd, 2023 at 08:57 pm

Many organic wastes can be used in the garden as valuable fertilizer. It is therefore obvious to also use coffee grounds or ash that accumulates anyway as an inexpensive fertilizer. But is this advisable and how do plants tolerate these substances?


Fertilizing with ash
The fine powder is very uncomplicated to produce yourself, because ash is produced as a residual product when firing naturally pure wood. It is important that you know exactly the origin of the fuel, as it can be heavily contaminated with pollutants depending on the source.

Coffee Grounds And Wood Ash: Are They Suitable Fertilizers?

Substances in the wood that are hazardous to health, such as varnishes or glazes, also accumulate when burned and can even poison the soil if you use the ash as fertilizer afterwards. Barbecue ash is also unsuitable, as it contains decomposition products such as acrylamide.

In the following table you will find the ingredients of pure wood ash:

Ingredient in percentQuantity
25 – 45Quicklime
3 – 6Maganesium oxide
3 – 6Potassium oxide
2 – 6Phosphorus pentoxide
Different quantitiesTrace elements such as iron, manganese, boron, sodium

Here we see one of the main problems that arises when fertilizing with ash: The fine powder is a grab bag, where you never know exactly how many nutrients are contained. Primarily, therefore, ash is applied to improve acidic soil. You can also sparingly fertilize some plants that are lime tolerant with ash:

  • Choose a windless day so that the white powder does not spread unintentionally throughout the garden.
  • Wear gloves to protect your skin.
  • For one square meter of soil, 100 to 400 g of ash, depending on the pH, is perfectly sufficient.
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Coffee grounds as fertilizer

Coffee grounds are a good fertilizer for all plants that prefer a moderately acidic to neutral soil environment:

  • It provides plants with ample nitrogen, resulting in improved growth of leaves and shoots.
  • Prepare the coffee grounds and let them dry well, as the moist powder quickly begins to mold.
  • Coffee grounds, which you simply scatter on the bed, does not show any fertilizing effect. For this, it must first be worked into the soil and decomposed by microorganisms and earthworms.
  • Coffee grounds are good for fertilizing grasses, as they prefer a slightly acidic environment. Again, spread dry and work in well.

Coffee grounds and wood ash should always be used judiciously. Unlike store-bought, organic fertilizers, you don’t know the exact composition and don’t have as good a handle on how they work. Therefore, dose sparingly and use both products in addition to other fertilizers.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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