How to Water Plants with Coffee

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Last Updated: July 16, 2023 References

No one likes to toss out leftover brewed coffee that turned warm. If you have a few acid-loving plants around, either in the garden or in containers, you can recycle the coffee into a nutritious treat that they'll love. Coffee contains quite a few nutrients which such plants will love, including potassium, calcium, nitrogen, phosphorous and other minerals.

Part 1

Part 1 of 2:

Checking the Compatibility of Coffee for Your Plants

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Research to see whether your plant is acid-friendly. Look up the type of plant that you have and see if it correctly digests acidic products. Many herbs and indoor plants will be suitable for this liquid coffee treatment. These are some examples that you can spray a coffee mixture on:^{[1]
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- Spider plants
- Roses
- Hydrangeas
- African Violets.
2
Use coffee grounds on other plants. As well as using up the liquid, there are ways to also get rid of the grounds that are beneficial for suitable plants. For example, you can combine coffee grounds with soil, compost or fertilizer.^{[2]
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Research source} These products can then be given to plants such as the following, to boost their growth:
- Lettuce
- Gardenias
- Azaleas
- Hibiscus.
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Part 2

Part 2 of 2:

Making and Applying the Coffee Mixture

Decide if you wish to brew a normal batch or a strong mixture, as this will determine how much water you will need to use later.^{[3]
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Consume, save, or discard any coffee that has been mixed with sugar and/or cream.
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Dilute the coffee.^{[4]
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Research source} Combine about 1/2 cup (120 ml) of water more than coffee as a standard mixture.
- For example, if you have 1 cup (240 ml) of leftover coffee, mix it with 1 1/2 cups (350 ml) of water.
- The amount of water can be more or less, depending how strong the original coffee is.
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Water the plants. Select one day out of the week to apply the diluted coffee on the plants. Coffee can be quite acidic, so you will only need to use it sparingly versus natural water.
- Start out small. It is better to give just a little and work out what your plants respond to than to overdo it and cause the plant to react poorly. You can slightly increase the dosage until you consider it is sufficient.
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If I'm not supposed to water leaves on roses, should the coffee still be used?

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Watering the leaves is not an issue, since they grow outside and are exposed to rain. Powdery mildew is fairly common in roses whether you water the leaves or not.

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Can I spray coffee on my hot pepper plants?

Ninox

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Yes. Pepper plants need a lot of nitrogen, and coffee has a high concentration of nitrogen.

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Will coffee grounds help with compost for outside?

Ninox

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Yes, coffee grounds can be used inside and outside to add phosphate and nitrogen.

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Tips

More garden uses for coffee can be found at How to use coffee grounds in your garden.^{[5]
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It is also useful to know the pH of the soil, to avoid rendering it too acidic for the plant.

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