A Dirty Colloquy – Using Coffee Grounds in a Garden

A Dirty Colloquy – Using Coffee Grounds in a Garden

So grab yourself a cup of coffee and let’s talk some dirt!

Many well seasoned gardeners have tested using coffee grounds in a garden and have discovered a few, rather positive benefits. From balancing the pH levels and possibly running off the pests, to other important benefits that should also be considered.

Some of the bigger benefits, and important ones include:

  1.  Offering the extra bit of protection for the environment. Pesticides and commercial fertilizers are harmful and leave soil unhealthy while empty fertilizer and pesticide containers go from the garden into the garbage. This means not only have those products went into the garden soil, but the landfill soil as well. Think about the future of that soil. 
  2.  Also, not killing or harming the insects and animal life. With a naturally built-in ecosystem, hurting the insects could harm this complex network of life.  For garden health it’s best to use organic options that will help redirect them by using the companion planting method. Most insects are good for one plant or another.
  3. Last, is being economically friendly. If the estimated 700 million cups of coffee are being brewed each day in the US alone, then Americans are using tons of coffee grounds. This not only makes sense economically – it literally makes CENTS!

When you make your morning coffee, stop throwing those grounds into the trash and start putting them in a nice, clean bucket or in your compost bin along with the filters.

Saving your coffee grounds is an easy, free, and organic compost material that nourishes your soil.


So, Let’s Get Diggin’!Garden Tools Shovel Bucket Digging


Digging up some more dirt, I realized that the majority of people agree that used coffee grounds are neutral in pH, but some want to continue claiming they’re too acidic.

According to only one of the many studies out there, Oregon State University’s Extension Service produced a nice, to-the-point, fact sheet which dismisses the idea that coffee grounds are too acidic. The “fact” is that the acid in fresh coffee grounds are natural and water-soluble, which means that once brewed, this little troublemaker (acid) leaves the grounds and goes right into your cup .

However, not everything in a coffee bean actually makes it into your cup of jo. Along with other ingredients that remain in the coffee grounds is the aroma producing oils, and even small amounts of caffeine.

Comparing information with OSU’s Extension Service fact sheet, the Wisconsin State University Extension states:


Nitrogen-rich proteins needed for seed germination and growth comprise over 10 percent of the content in coffee grounds (Tokimoto et al. 2005). Since coffee is extracted in water, most of the hydrophobic compounds, including oils, lipids, triglycerides, and fatty acids remain in the grounds, as do insoluble carbohydrates like cellulose.


So, basically  once coffee is brewed and has undergone the process, the acidic level will have decreased, leaving the grounds at a more neutral pH.


“More coffee please? – The dirt’s getting good!


Coffee Talk Dirt In The Garden

Composting your leftovers…

Coffee grounds are a super source of nitrogen for your compost. If you’re a gardener, you probably already use your coffee grounds as a “must-have” in your compost mix.

You can begin composting, by first collecting coffee grounds from your morning coffee. You can also check with your local café and restaurants to see if they can save some as well. Start putting them into a clean 5 gallon bucket, or a nice 30+ gallon trash container. Park it next to your compost pile for a later, quick, and easy access.

To compost your coffee grounds, start layering your elements in equal parts, using a third of each of the following – leaves, fresh grass clippings, and used coffee grounds. You can also add your coffee filters, shredded newspaper, and other paper items that you might have laying around, as they’re all a great source of carbon.

By having your mixture outside; sitting for a period of time (several months), it allows for bacteria and fungi to break down the different chemical components that are nitrogen-rich – like proteins and caffeine.

By the end of the compost process, the carbon-to-nitrogen ratio you should look for, ideally, is 10:1.

Some people might think that during this process, their coffee grounds are going bad. Don’t worry – they’re not! Coffee grounds do not go bad, according to the “fact sheet” from OSUES.


The earthworm conundrum…

In general, a friend of the compost is the earthworm.

Although it has been a speculation that coffee grounds attract the earthworm, there is no science-based information that supports the idea that the coffee grounds actually benefits them. However, it is noted that earthworms, as well as other bio-consumers of the ground, do use coffee grounds as a source of food.

Also, because earthworms pull the coffee grounds deep into the dirt, that may be what accounts for the noted improvements in the soil structure, after the coffee grounds were applied.


Black Gold! – I’m feeling rich :o)


Using Coffee In A Garden Beans

This rich, dark compost can be used either by tilling or working it into the soil, or simply by using it as a nutrient-providing mulch. Either way, through studies and experiments, the results have shown positive effects in the soil.



Like all good mulch, using coffee grounds in a garden help maintain the soil temperature.

When using as a mulch, only apply about one half inch of coffee grounds; topping it with about 3-4 inches of wood chips. This will prevent the coffee grounds from compacting or drying out. Dry, compacted grounds will stop the water and nutrients from getting to the plants.


In the garden

There is much documented evidence that indicates, you can combine approximately 30% coffee grounds with any type of mineral soil to improve it’s structure.  With that being said, the better way to get the job done is by working the grounds into the soil with a tiller or cultivator. To get the coffee grounds thoroughly mixed in, you will need to till approximately 6 to 8 inches deep into the soil.

Combining the coffee ground compost  into your garden, will help improve the phosphorous and potassium, as well as the magnesium, calcium, and copper minerals.

This 9 Step Guide can help you get started.


Become Master GardenerPlants and Pests

Plants like coffee grounds. Especially tomatoes and roses. But those aren’t the only ones that enjoy getting their share of delisciousness. Others include hydrangeas, azaleas, and even watermelons! Yes, watermelons. Watermelons love the hot rich soil. Actually, the hotter the soil, the better the melons.

Back in her elementary school days, my niece decided she wanted to grow watermelons outside her back door. A few weeks after planting them, she decided to start using coffee grounds, and began working them into the soil, around the plants, with her fingers. When it came time to harvest, they were so delicious – super sweet, and very juicy.

Also, one of the locals in my home town uses used coffee grounds in his garden. He agrees that they are beneficial in growing his vegetables and because he gets them from local coffee shops, they’re a great way to recycle.

It is important to know also, you don’t apply coffee grounds in areas where you are growing plants from seeds. This can cause reduced seed germination and in some cases, reduced plant growth.

Last, a pest can be your pal. If you plant, using a companion planting method, you will see results of pests hard at work – in a good way! Among everything, there is good and bad. As for the garden pests, that is equally true.

To sum things up, whether tilled into the soil or used as a mulch material, coffee grounds have been proven to have a positive effect on garden soil. Don’t waste a chance to feed your plants!

Please share this article with family and friend or anyone you feel might benefit! Feel free to leave a comment, sharing your thoughts about using coffee grounds in a garden.

Thanks so much. – Paula

12 thoughts on “A Dirty Colloquy – Using Coffee Grounds in a Garden”

  • What an interesting article, I can remember much grandmother always saving the coffee grounds and tea leaves for the compost bin.
    Now I know why.
    Thank you Mark

    • Thanks for your comment Mark! A super idea. I have to say, folks back in the day knew exactly what they were doing, haha. Have a great day and thanks again!

  • Thank you so much for the tip. I have been drinking coffee all these years and can’t believe it has never occurred to me to use the grounds for my plants! I am definitely going to save them from now on.

    • Thank you for the comment. It sure is a great deal! I haven’t decided if it’s more like a BOGO sale or a piggy bank where you can put your goodness in and take it out later. I think both suit the situation :o). Either way, it’s a WIN-WIN. Thanks again; I sure enjoyed you stopping in!!

    • Thank you for sharing that!!! You know, I had read that too, but because I also read there were no actual “science related” evidence of this, I kind of kept it to the back of my thoughts. Where I live, there are many homeless cats so this is very helpful :o). Thank you!

  • My wife has been wanting to start a garden for some time now. We had inherited a small one in our old house (the previous owner had obviously been a big fan of tending her yard and garden), but since we moved, we’ve been without. I really wouldn’t have thought about using coffee, and truthfully I don’t even drink it, but my wife does on occasion. I;ll have to mention this to her.

    I am curious about the compost though… Our only real experience with composting comes from the fact that where we live we now have to split our garbage and compost for pickup by the city. I am happy to do so, but boy, does the bin ever start to smell, especially in the summer. If it smells so bad after only a few days (it’s picked up weekly), wouldn’t having a larger bin in one’s back yard become somewhat overwhelming? To say nothing about the flies….

    When we moved in here, the previous owners had left a bag of grass clipping in the driveway at the side of the house. Being a paper bag that had been out in the rain, when I tried to move it, it split open and the stench was so overwhelming that even holding my breath, I was struggling not to vomit. How does one deal with that? Do you simply keep it at the far end of your yard?

    I’m not trying to be critical; I think composting is an awesome thing, but I don’t understand all the ins and outs of it.

    • Hi Craig and thanks for your comment! Haha … WOW! Sounds like you had a tough time there with the old clippings. I currently do not have a compost, but have been considering so for a bit. I use to have a neighbor that had one, and they would use a big fork and keep theirs turned. I never noticed it smelling. I suppose if you just leave it sit, letting it rot, it might be a bit stinky. I’m like you, the composting part I would need practicing. Definitely in on the to-do and wish list for me. Thanks again :o)!

  • Hi Paula,
    It may not be very scientific, but my father always made us throw the coffee grounds out in the garden. He told us it was good for the earth worms. He loved to fish and his bait of choice was night crawlers, as he called them. You know, the big juicy worms fish love to eat? I can remember going out in the garden with our flashlights, after a summer rain, and “picking night crawlers”. We always had an abundance and Dad said it was because of all the coffee grounds. Science may not agree, but I’d like to think “father knows best.” 🙂
    Thanks for sharing!

    • Hi Kathy and thanks so much for stopping in to share your story! Haha, I agree… FATHER KNOWS BEST! I’m not one to go night crawler hunting, cause I’m squeamish of worms, haha. But, I do understand the need for fishing with them, as I have a couple of sons that enjoy this sport. Anyway, thanks again for the comment Kathy, and I sure look forward to seeing you again here in the garden :o). – Paula

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