Can My Leftover Coffee Be Used to Water Plants? (2024)

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A weekly feeding with leftover coffee provides nitrogen

Colleen Vanderlinden

Colleen Vanderlinden is an organic gardening expert. She wrote the books Edible Gardening for the Midwest and Vegetable Gardening for the Midwest, and her writing has appeared in Mother Earth News, Northern Gardener, The Detroit News, and Birds & Blooms.

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Updated on 04/08/23

Reviewed by

Mary Marlowe Leverette

How Often to Water Plants With Coffee

Though it's tempting to pour what's left in your daily cup of coffee into your plants, it's best to stick to fertilizing with coffee once a week. If you decide to try watering houseplants or outdoor plants and vegetables with coffee, keep a close eye on your plants. If foliage starts yellowing or the tips of the leaves start turning brown, it's a sign that the coffee is adding too much acidity to the soil, or that you have to cut down on how often you water your plants with coffee or coffee grounds. Try feeding plants coffee once every two to four weeks and see how your plants tolerate the reduced schedule.

Coffee-Loving Plants and Vegetables

Plants that prefer more acidic soil may respond well to a weekly watering with coffee or sprinkling of coffee grounds. But take into consideration the plants that may prefer slightly acidic soil vs. plants that like very acidic soil. For example, roses and beans may prefer only very slightly acidic soil but blueberries prefer more acid. Here is a list of both indoor and outdoor plants that would love a sip of your leftover coffee:

Houseplants:

African violets
Phalaenopsis orchids
Dieffenbachia
Norfolk Island pines
Nerve plants

Outdoor plants, trees, and shrubs:

Azaleas
Rhododendrons
Siberian iris
Lupine
Impatiens
Pine trees and shrubs
Holly bushes
Magnolia trees
Roses
Lilly-of-the-valley

Vegetables and fruits:

Blueberries
Potatoes
Cucumbers
Peppers
Carrots
Radishes
Beans

Using Leftover Coffee Grounds

Can My Leftover Coffee Be Used to Water Plants? (4)

Coffee grounds can be a good source of nitrogen in your compost pile or when added directly to the soil in the garden. If added in fairly large amounts, they can raise the acidity level of the soil for acid-loving plants. Coffee grounds sprinkled over the ground around acid-loving plants serve as a mild acidfertilizerfor them.Worms seem to love them, either in your garden or outdoor compost pile or in a vermicompost bin.

Coffee grounds are regarded as an effective natural deterrent to garden pests such as slugs, snails, and ants. Rumors of coffee grounds repelling deer may be overstated. Deer are voracious eaters, and a few cups of coffee grounds are unlikely to make much of a difference. Coffee grounds will discourage a mischievous cat from roaming in your garden, but their effectiveness on rabbits and other common garden rodents is unknown.

Tip

If you're not a coffee drinker, don't forget your used tea leaves. They work great as a soil enhancer around acid-loving plants and add nutrients to compost piles.

How to Use Leftover Liquid Coffee

Can My Leftover Coffee Be Used to Water Plants? (5)

When using leftover liquid coffee for plants, it is a good idea to first dilute your coffee with more water, especially if you prefer your daily cup of java on the strong side. But consider that in some workplaces, the only "watering"plants received is from emptying leftover coffee into the soil, and they often do quite well.

Tip

Liquid coffee can also be used to water a compost pile that has become too dry.

FAQ

Which plants like coffee as a fertilizer?
Acid-loving plants, such as azaleas and blueberries, love coffee. However, tomatoes and lavender may not fare well if you use coffee to fertilize them. Be sure to check to see if your plant prefers acidic soil before using coffee or coffee grounds as fertilizer.
How often can you water plants with leftover coffee?
You should only water plants with coffee once per week. Keep that leftover coffee from the carafe in another container to use weekly.
Can I sprinkle coffee grounds in my garden?
Coffee grounds work well as a fertilizer for many plants and their soil. Just sprinkle the coffee grounds on the soil around the plants.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Grounds in the Garden. Texas A&M University AgriLife Extension.

As a seasoned gardening expert and enthusiast, my wealth of knowledge in organic gardening allows me to delve into the intricate details of utilizing coffee in gardening practices. The article in question, written by Colleen Vanderlinden, an esteemed organic gardening expert, and reviewed by Mary Marlowe Leverette, a Master Gardener with over 30 years of experience, provides valuable insights into the use of coffee for plant care. The fact-checking by Emily Estep, a plant biologist and journalist, further underscores the reliability of the information presented.

Now, let's dissect the key concepts covered in the article:

1. Coffee as a Nitrogen Source:

Expert Insights: The article suggests that using leftover coffee or coffee grounds in gardening provides a source of nitrogen. This is crucial for fertilizing certain indoor and outdoor plants.
Best Practices: It emphasizes the importance of using only black, unflavored coffee for this purpose.

2. Frequency of Coffee Application:

Expert Advice: While it might be tempting to use coffee daily, the article advises against it. Instead, it recommends a weekly application to avoid potential issues like yellowing foliage or browning leaf tips.

3. Plants Benefiting from Coffee:

Expert Knowledge: Different plants have varying preferences for soil acidity. Acid-loving plants, such as azaleas, rhododendrons, and blueberries, may benefit from weekly coffee watering.
Plant Examples: The article provides a comprehensive list of indoor plants (African violets, orchids, etc.), outdoor plants (azaleas, pine trees, roses, etc.), and vegetables/fruits (blueberries, potatoes, peppers, etc.) that can thrive with a sip of leftover coffee.

4. Using Coffee Grounds:

Expert Tips: Coffee grounds are highlighted as an excellent source of nitrogen in compost piles or when directly added to the soil. They can also raise soil acidity for acid-loving plants.
Additional Benefits: The article mentions that worms are attracted to coffee grounds, and they can act as a natural deterrent to pests like slugs and snails.

5. Liquid Coffee Application:

Expert Guidance: Diluting leftover liquid coffee with water before application is recommended, especially if the coffee is strong.
Alternative Use: The article mentions that liquid coffee can also be used to water a dry compost pile.

6. FAQs:

Expert Answers: Common questions are addressed, such as which plants benefit from coffee (acid-loving plants) and how often one should water plants with leftover coffee (once per week).

7. Tea Leaves as an Alternative:

Expert Advice: For non-coffee drinkers, the article suggests using used tea leaves as a soil enhancer for acid-loving plants.

8. Fact-Checking and Credibility:

Rigorous Process: The article emphasizes that The Spruce uses high-quality sources, including peer-reviewed studies, to ensure accuracy, reliability, and trustworthiness.

In conclusion, the article not only showcases a depth of knowledge in organic gardening but also benefits from the collective expertise of individuals with extensive experience in horticulture and plant biology, reinforcing the credibility of the information presented.