Using coffee grounds for plants has advantages and disadvantages.

Many plant lovers who drink coffee are using coffee grounds as a fertilizer and to add to compost. But there’s confusion on when, where, how — and whether — to use coffee grounds for best results.

If you don’t drink coffee, there are options for easy access to lots of used coffee grounds via local coffee shops and restaurants. If we consider the widespread habit of drinking coffee, we can imagine the huge amount of available coffee ground resources.

Making Good Use of Spent Coffee Grounds (SCG)

Most gardeners love to recycle, upcycle and compost as much as possible, and coffee grounds are one of those items with fringe benefits. Even if it’s just one or two people in your home consuming two cups of coffee a day from fresh coffee grounds, the refuse of spent coffee grounds (SCG) can really add up over time.

We’re coffee fans and have added organic coffee grounds to our compost pile along with other organic matter for years now. We love how the coffee beans that create our favorite brew can go onto benefit our plants too! But we wanted to know more on using coffee grounds for plants and gardening.

So we started researching things like what plants like coffee grounds in the soil as fertilizer, and which plants don’t? And should we put the coffee grounds directly around the plants that like coffee, or should we continue putting the coffee grounds into the compost?

That’s what we wanted to know for sure. However, as we studied this topic of using coffee grounds for plants, we were surprised at what we found.

The deeper we dug into the info and research, the more we discovered the complexity of the subject. The more we learned, the more questions we developed.

It’s not as simple as a list of what plants like coffee grounds, and what plants don’t. When it comes to plants and plant ecosystems such as in the garden, what’s seemingly good for one thing could be compromised by another.

It’s a Complicated Relationship

It turns out that some of the research on using coffee grounds for plants runs contrary to urban legend. The relationship between coffee and plants is complicated, but we’re going to try to keep it as simple as possible.

So grab your cup of joe and let’s go!

Confusion and Misinformation

In researching this article, we found a LOT of content that was basically copying the same content over from other websites. Okay, so everyone’s saying it… it must be true, right? Haha… you know better too, don’t you!?

Yep, proliferation of content, doesn’t necessarily mean that it’s true, especially if it’s repeating the same misinformation.

We began our journey down the rabbit hole on using coffee grounds for plants because we kept finding conflicting information.

Some articles say never to use coffee grounds in the garden. Others say that coffee grounds are wonderful for plants.

Some lists of what plants like coffee grounds had exact opposite recommendations to others. In other words, one plant might show up on the “likes” list of one website and the “does not like” list on another. In addition, there was conflicting information on the acidity of coffee grounds, nitrogen benefits, caffeine detriments, and whether coffee grounds are a fertilizer, amongst other details.

Hmm… okay, this isn’t going to be a quick and easy article to write after all.

Time to Dig Into Scientific Studies on Using Coffee Grounds for Plants

Time to roll up the sleeves and cut through the noise and confusion. We like to go to scientific research studies whenever possible, and that’s where we found the most interesting, informative, and relevant information on this subject. Even though there was some conflicting information on some of the extension service articles, overall, we were able to glean the bigger picture to share with you here in this article.

In doing all that research, we also discovered several reasons for the confusion and misinformation on using coffee grounds for plants. We’ll list that shortly, at the end of this section or so.

So now that we’ve got it all sorted out, hopefully it will be much easier for you to read and heed for the best results for your plants.

But in gardening, as in life, learning isn’t a one-and-done. It’s an ongoing daily process, so if you have additional facts or personal experience to share, send it on, we’d love to learn from you too!

First, we wanted to know:

Are Coffee Grounds Acidic?

No, not really. Spent coffee grounds are NOT highly acidic.

Apparently, while coffee is an acidic beverage, used coffee grounds are not considered to be acidic. Many articles will say that coffee grounds are acidic, and some will say that they’re highly acidic.

However, that’s not true.

Research on pH levels of coffee grounds for plants and in the soil over time is they they are either mildly acidic or mildly alkaline, and any acidity declines to neutral over time and never affects the entire soil pH.

The reason coffee grounds are not acidic is because the acid in coffee is water soluble, which means that most of the acid in coffee ends up in your cup of coffee and not the grounds, and therefore not in your soil either.

The perfect pH balance is 7.0, with a mild mid range on either the acid or alkaline side of 6.5-7.5. Spent coffee grounds, also known as (SCG) in research studies, typically registers between 6.5-6.8 pH, and moves towards mildly alkaline over time.

“The pH of decomposing coffee grounds is not stable and one shouldn’t assume that it will always, or ever, be acidic.”
~Linda Chalker-Scott, Ph.D., MasterGardener WSU editor, Extension Urban Horticulturist^[1]http://www.uwyo.edu/barnbackyard/_files/documents/magazine/2017/summer/plantsperk0717.pdf

Why Many Lists on What Plants Like Coffee Grounds Are Not Relevant

If you’re wondering what plants like coffee grounds, well, it turns out that it doesn’t really matter that much, which we will explain as we continue.

Most articles you’ll find on page one of Google listing what plants like coffee grounds and what plants don’t, are based on which plants are acid loving plants, and which ones are not.

It’s seems logical that since coffee is an acidic beverage, the coffee grounds would also be acidic. So the confusion and misinformation is understandable. However, as indicated above, that isn’t the case when it comes to spent coffee grounds.

Soooo… it doesn’t matter which plants do — or do not — like acid, because coffee grounds are essentially pH neutral.^[2]https://extension.oregonstate.edu/gardening/soil-compost/coffee-grounds-composting

Now we have some new questions to ask and answer, which is what we’ll do next. Are coffee grounds good for plants, how and which plants? Let’s take these questions one at a time.

3 Easy Ways to Test Your Soil

If you need to test your soil, here’s three simple ways:

• Your weeds will reveal your soil health!
• Perform a simple soil sample test
• Ask the county extension service to test it for you, (that’s usually a free service).

So Are Coffee Grounds Good for Plants?

Yes… and no. We’ll start here with how coffee grounds are good for plants.

Coffee grounds do have nutrients beneficial to plants. But more than that, it’s that coffee grounds are good for the support systems that help plants grow.

Soil tilth is the structure of soil, and includes the consistency, composition, aeration and permeability of soil.

Benefits of Coffee Grounds in the Garden and Farm Crops

• NUTRIENTS:
  • Proven to increase iron and zinc levels in the rice crops grown with coffee and tea waste^[3]https://pubmed.ncbi.nlm.nih.gov/21547921/
  • An organic plant supplement, but does not replace a good organic fertilizer
• WEEDS: Natural weed control for developing crops^[4]https://www.tandfonline.com/doi/full/10.1080/1343943X.2021.2007142#
• DISEASE: Disease suppression during decomposition – coffee grounds in soil help suppress common fungal rots and wilts such as Fusarium, Pythium, and Sclerotinia, which typically affect:
  • potatoes
  • tomatoes
  • peppers
  • eggplants
  • herbaceous plants
  • succulents
• SOIL:
  • Retain moisture in soil, (but only if applied as a thin mulch so as not to create a water barrier)
  • Helps regulate soil temperature
  • Improves soil tilth
• PEST DETERRENT:
  • Gets rid of ants – based on comments from readers from their direct experience
  • May get deter voles, moles or chipmunks (based on the observation of one gardener which you can read more about in this voles article)
  • Some believe that coffee grounds may deter slugs and snails* 

Coffee grounds help retain soil moisture.

*For mulch, we prefer free wood chip mulch.

**We’ve not found scientific research to verify the coffee grounds for slug riddance folk remedy. This article on how to get how to get rid of garden slugs includes a video that does appear to show that some slugs and snails seem to avoid the coarse matter, either due to odor or texture. However, the results are not scientific, nor consistent enough in a subsequent test to be conclusive as yet.

SOURCES:
SCGs could be effective agricultural materials for weed control, and the weed control potential of SCG application has been demonstrated (e.g. Kito & Yoshida, 1997).

Coffee grounds add tilth to the soil, nurture soil microbes, and suppress plant fungi and weeds, but can also stunt plant growth!

Nutrients in Coffee Ground

Coffee grounds contain nitrogen, phosphorus, and potassium, which are three major nutrients needed by most plants to grow.

As indicated earlier, coffee grounds are not actually acidic. Spent coffee grounds range between mildly acidic to somewhat alkaline when added to soil or compost. As coffee grounds decompose the pH tends toward neutral or even toward mildly alkaline.

Coffee Ground Macro Nutrients by Volume

• 2% Nitrogen
• 0.06% Phosphorus
• 0.6 % Potassium

Coffee Ground Micronutrients

• Boron
• Calcium
• Copper
• iron
• Magnesium
• Zinc

Reference: University of Wyoming, Summer 2017 Newsletter, article by Lisa Ogden in Barnyards & Backyards

What Plants Like Coffee Grounds?

In case you jumped to this section and didn’t read the preceding paragraphs, it’s important to let you know that the following lists include plants that are often cited as benefitting from spent coffee grounds. We’re sharing these lists here because, well, that’s what we set out to do, and you’ll find varying degrees of these lists on other websites.

However, please note that most lists you see are created under the misunderstanding that coffee grounds are highly acidic. Since that turns out not to be true, some plants can benefit from coffee grounds in small quantities, but, the caffeine content in coffee grounds may actually retard plant growth!

Reasons Plants Like Coffee Grounds in the Soil – It’s NOT the Acidity!

1. Improves soil tilth
2. Benefits soil microbes
3. Reduces fungi

That said… for the record, here are some lists of acid loving plants.

Acid Loving Plants

Flowers That Like Coffee Grounds

• African daisies, Dimorphotheca ecklonis, (pH 5-5.5)
• Begonias
• Cyclamen
• Daffodils
• Gladiolus
• Hyacinth
• Impatiens
• Nasturtiums
• Roses – benefit from the microbes that help suppress fungal rot and wilt such as Fusarium, Pythium, and Sclerotinia

RELATED: You may enjoy this article on purple flowers.

Fruit and Fruit Trees That Like Coffee

• Blueberries
• Citrus trees
• Meyer lemon trees – pH between 5.5 and 6.5
• Pineapple plants, Ananas comosus, is a bromeliad in the bromeliaceae family

RELATED: More on citrus trees: growing dwarf Meyer lemon trees.

14 Garden Plants That Like Coffee Grounds in the Soil

The truth is that coffee grounds aren’t nutritious enough to be considered a fertilizer all by itself. However, coffee grounds can be akin to a plant supplement, with subsequent benefits.

1. Blueberries
2. Carrots
3. Eggplants
4. Gooseberries
5. Hydrangeas
6. Lily
7. Maidenhair fern
8. Parsley
9. Peppers
10. Potatoes
11. Radish
12. Rhododendrons
13. Strawberries
14. Tomatoes

Do Houseplants Like Coffee Grounds?

Not exactly.

The best way to use coffee grounds for indoor houseplants is as coffee grounds “tea”, rather than actual coffee grounds. Coffee grounds added directly to your plant soil, won’t add much acidity, because of the water soluble nature of the acidity in coffee.

Reasons not to Use Coffee Grounds on Houseplants

• Messy and coffee grounds will mold, and likely attract fruit flies and other insect.
• Give coffee, not grounds – any potential nutrients and acidity in used coffee grounds are better derived through making coffee grounds “tea” and watering the plants with it.

You can find more on coffee grounds for houseplants in this article on RealSimple by Kim Toscano, if that’s your interest. We were delighted to be mentioned in that article as well.

Coffee Grounds Tea

We have a recipe below for making coffee grounds tea for watering your plants. add water to used coffee grounds, steep for a few hours or a day or so, and then strain and water the plants with the coffee water. We could find no studies on the pH content on this recycled coffee grounds water, however it stands to reason that used coffee grounds would have diluted quantities of the same nutrients.

If you’re wondering what houseplants are known to respond positively to coffee grounds, check out this list to see if your houseplants are included.

25 Indoor Houseplants That Like Coffee

A neutral soil pH is 7.0. Most houseplants thrive in the slightly acidic to neutral range of pH 6.0 to 7.0.

Some plants in this list of acid loving indoor plants can also be outdoor plants in summer or in favorable hardiness zones.

1. African violet, Saintpaulia spp., (pH 5.8-6.2)
2. Aloe vera, Aloe barbadensis miller, (pH 4.5-5.5)
3. Avocados, Persea americana, (pH 5-7) (See avocado leaves uses and benefits)
4. Begonias, in the Begoniaceae family(pH 5.2-6.0)
5. Boston ferns, Nephrolepis exaltata, (pH 4.0-6.5)
6. Bromeliads, Bromeliaceae, (pH 4.0-7.0)
7. Cactus plants, Cactaceae (pH 5.0-7.0)
8. Christmas cactus, Schlumbergera bridgesii, pH of 5.5 to 6.2
9. Cyclamen, Cyclamen persicum, (pH 5.8-6.0)
10. Dragon Tree, Dracaena marginata,(pH 6.0-6.5)
11. Fuchsia, Fuchsia magellanica, (pH 6-7)
12. English ivy plants, Hedera helix (pH 5.5-6.5)
13. Geranium, Pelargonium (pH 6.0-6.5)
14. Golden Pothos, Epipremnum aureum, (pH 6.1-6.5)
15. Hibiscus, Hibiscus, family Malvaceae (pH 6.5-6.8); see our favorite Hibiscus Fiesta
16. Jade, Crassula ovata, (pH 6.0-7.5) (can be acidic to slightly alkaline)
17. Janet Craig, Dracaena fragrans, (pH 6.1 to 6.5)
18. Meyer Lemon Tree, Citrus × meyeri (pH 5.5-6.5)
19. Monsteras, Monsteras (pH 5.5-7.0)
20. Orchids, Orchidaceae family, (pH 5.5 and 6.0)
21. Peace Lily, Spathiphyllum, (pH 5.0-6.5)
22. Peperomias, Peperomia obtusifolia (pH 5.0-6.0)
23. Philodendrons, Philodendron bipinnatifidum, (pH 5.0-6.0)
24. Snake plant, Sansevieria trifasciata, (pH range of 4.5 to 8.5; ideal pH of 5.5-7.5) (can be acidic to slightly alkaline)
25. Spider plant, Chlorophytum comosum, (pH 6.0-6.5)
26. Succulents, (pH range 4.0-6.5; ideal pH 5.5)

7 Shrubs that Like Coffee

7.0 is neutral, so most of these shrubs are acid loving plants.

1. Azaleas, greenhouse azaleas, Rhododendron sp., (pH 4.6-6.0)
2. Blueberries, (highly acidic at a soil pH 4.2-5.0)
3. Camellia, Camellia japonica, (pH 6.0-6.5)
4. Crotons, Codiaeum variegatum, (pH 4.5-6.5)
5. Gardenia, Gardenia jasminoides, (pH 5.0-6.5)
6. Hydrangea, Hydrangea macrophylla, (pH 5.2-5.5)
7. Mountain heather, Cassiope, (pH 4.5-5.5)
8. Rhododendrons, (Rhododendron), (pH 4.5-6.0)
9. Roses, miniature roses, Rosa chinensis minima, (pH 6.5)

Trees that Like Coffee Grounds

There are a number of evergreen and deciduous trees that love coffee grounds. Here are some examples:

• Evergreen trees, including:
  • Norfolk island pine, (Araucaria heterophylla)
• Deciduous trees including:
  • beech
  • dogwood
  • mountain ash
  • magnolias
  • oak
  • willow

Which Plants do NOT Like Coffee Grounds?

Apparently, it’s the caffeine in coffee that can stunt the growth of weeds (yay!) and some plants (uh-oh!).

Here is a partial list of plants researched in one study that did NOT like coffee grounds or coffee as fertilizer, in fact their growth was stunted compared to a control group grown without coffee grounds

• Broccoli
• Leeks
• Lettuce^[5]https://extension.oregonstate.edu/gardening/soil-compost/coffee-grounds-composting
• Radish
• Sunflower
• Viola

REFERENCES:
Urban Forestry Study, Sarah J. Hardgrove, Stephen J. Livesley 2016
GrassRoots Garden in Eugene, OR, germination test of coffee grounds for lettuce^[6]https://extension.oregonstate.edu/gardening/soil-compost/coffee-grounds-composting

Issues With Using Coffee Grounds for Plants

There is a significant proven disadvantage to using spent coffee grounds in the soil for garden plants: studies show that using coffee grounds in the garden or agricultural crops can actually slow plant growth!^[7]https://www.tandfonline.com/doi/full/10.1080/1343943X.2021.2007142#

While retarding the growth of weeds you don’t want is helpful, slowing the growth of your plants is NOT what gardeners and farmers want for their garden plants.^[8]https://pubag.nal.usda.gov/catalog/5272385

So basically, those lists won’t really make a difference for you, since most lists on what plants like coffee are citing acid-loving plants. And well, if you missed it, take a stroll through the paragraphs above to get the bigger picture that we discovered anent that.

It’s important to know the negatives in using coffee grounds for plants in the garden.

4 Disadvantages of Spent Coffee Grounds for Plants:

1. RETARDS PLANT GROWTH: Coffee grounds have been proven to slow plant growth.^[9]https://pubag.nal.usda.gov/catalog/5272385
2. REDUCED GERMINATION: Coffee grounds reduce the germination of plants grown from seed as amendment or mulch.
3. MAY REDUCE WORM POPULATION: There are conflicting studies on this, each indicating the opposite results, so more studies are needed:
   • One study of 3 different test mediums and environments, found SCGs to reduce worm population between 15-80%!!^[10]https://www.researchgate.net/publication/51249148_Evaluation_of_three_composting_systems_for_the_management_of_spent_coffee_grounds
   • Another study indicated an increase in vermiculture!!^[11]https://www.researchgate.net/publication/262804836_The_potential_of_coffee_grounds_and_kitchen_waste_in_vermicomposting
     NOTE: See contributor comments below to learn directly from readers as to their experience.
4. MAY LEAD TO NITROGEN DEPLETION: More research is needed as once again, we found conflicting studies and information on this:
   • Nitrogen depletion: SCG is not a fertilizer, and can even lead to nitrogen depletion as nitrogen loving microbes consume the small nitrogen contributions from SCG before your plants can. Subsequently, using coffee grounds requires the addition of a nitrogen fertilizer.^[12]https://extension.oregonstate.edu/gardening/soil-compost/coffee-grounds-composting
   • Nitrogen Beneficial: However, another study showed an increase in nitrogen when using a coffee grounds mix for vermiculture.^[13]https://www.researchgate.net/publication/262804836_The_potential_of_coffee_grounds_and_kitchen_waste_in_vermicomposting

There are a number of articles citing coffee grounds as beneficial to worms. However, those that we scoured did not provide substantiating research, so more research (or time to peruse existing research), is needed.

Add Cardboard and Paper to Vermiculture Along With Spent Coffee Grounds

The first study cited above in bullet #3, indicated that in one control where torn or shredded cardboard was added to the compost mix, the worm population declined the least of the three.

So if you’re using coffee grounds in your compost bins, it will help your worm population to include some shredded cardboard and paper, including drip coffee filters if you use them.

If you’re concerned about possible bleach in the filters entering your compost, it’s not thought to be a hazard.^[14]https://perfectdailygrind.com/2017/08/the-great-paper-coffee-filters-debate-bleached-vs-unbleached/

Variables in Research Happen

When it comes to gardening, while there are general rules that tend to apply, whenever you’re dealing with a variety of organic variables, it’s understandable that what works for one, may be completely opposite for another. So it helps to remain open to ongoing learning through experimentation to test theories and advice, old and new.

Contributions from the Community – Your Voice of Experience Counts!

Given that different environments, elements and practices are at work in any garden, we believe that your tried and true experience from years doing your own hands-on gardening is equally valuable. So please share your experience and observations of what’s working in your garden.

If you use spent coffee grounds in your soil, compost or vermiculture, and your worm population is thriving (or declining), please let us know.

If you’re not interested in these tips from the field, so to speak, you can jump to the next section on how to use coffee grounds for garden plants.

Contributions from GardensAll Readers With Experience of Coffee Grounds and Worms

Elly-Mae Smith – Worms Made Their Home in Coffee Grounds

“I sometimes get the huge bags of coffee grounds left over from our local coffee shop and one year a bag had been put out by the garden waiting for me to empty it. Anyway somehow it got forgotten about for about 6 months! When I came across it and opened it up it was literally completely full of garden worms!!! Not sure how this happened but I’m tempted to try it again! There was ONLY coffee grounds in the bag so??? Hope this information is helpful.” 
~Cheers, Elly, gardener in New Zealand

YES that is helpful, Elly! Wow! That some very strong anecdotal evidence that worms like coffee grounds. Yours chose it and claimed it! Thanks for sharing.

Jackie Kaizar – Trench Composting With Coffee Grounds and Lots of Worms!

“I’ve been gardening for over 40 years and always compost coffee grounds (with filters) along with table scraps directly into the garden (trench composting).  Even though I have partial shade, I have had a very successful harvest.  And much to the delight of my fisherman grandson, many worms.  After harvest, I trench the garden and add my table scraps and grounds until the soil freezes and then continue after the thaw until planting time.  Occasionally I add peat moss.”  

Janine Morris – Worm Are Thriving in Coffee Grounds!

I live in central Florida 2 mins from the west coast. We have extremely sandy soil. I use the term soil loosely. Haha.

When we moved in 10 yrs ago I added cow manure and 2 little fishing sized tubs of earthworms to the yard. I have watched them thrive and struggle.

Right now since I have been using the coffee grounds for 1.5 yrs now the worms are thriving.

We had hammerhead worms for a while which hurt the earth worm population.

I know this because I homeschool my daughter and she regularly digs in our yard, under every rock, under every planter and we have a great idea how many bugs there are and which kinds. 

Hope this helps,
~Janine Morris, Hobby gardener

Yes indeed! Thank you for sharing your tried and true experience, and congratulations on your efforts to transform your sandy yard into a more habitable one for more plants❣️

Kathy Brown – Home vermiculture Container – Coffee Grounds for Worms Works!

I had a home vermiculite container and used coffee grounds in it every day.  Never had an issue, that I know of, with declining worm population.  I had so many worms that I just had to get rid of them every now and again. 

Hope that helps!
~Kathy Brown, gardener, vermiculture

Yes it does! Thanks for sharing your experience of coffee grounds and worms!

Kim Oswald – What Grandma Knew About Coffee Grounds and Worjs

As a child I loved to dig for worms. I used my mother’s sterling silver spoons.

I was told by my grandmother who loved to fish, to put coffee grounds in the same area and I’d have lots of worms. She was correct.

I live in an area where fishing is prominent and spent coffee grounds are used to get a bumper crop of worms. I have bought worms that were sold in containers of spent coffee grounds.

I also have a friend who raises worms and he uses spent coffee grounds in his growing medium. Now it might have been the coffee grounds or maybe it was my mom’s good sterling spoons but it’s always attracted worms for me.🐛🐛🐛
~Kim Oswald, gardener

Larry Johnston – Coffee Grounds in Compost

I read with interest your report on using coffee grounds in the garden. I have been using them for the past twenty years and am happy with the results.

I use them mainly in my compost. I have a 4x4x4 ft compost bin.

1. Each fall I fill it 80% with ground up leaves and garden refuse.
2. Then I collect coffee grounds from a local coffee shop and turn the compost.
3. I layer in the coffee grounds and dampen each layer until the bin is full.
4. I turn the compost few times and it usually heats up.
5. Soon there are lots of red wigglers in it especially around the edges where it is cooler
6. After one year I transfer the semi finished compost to another bin. I have a few plastic composters and use them as worm bins.
7. I use the semi finished compost as bedding and add my household scraps and some water. The worms do well there.
8. I harvest the compost the next spring, and spread about 1/4 inch layer over the garden and have good results.

Thanks for your report. I hope this info is useful.

I don’t think the worms are adversely affected by the coffee grounds, in fact there seem to be more of them where there are more coffee grounds.
~Larry Johnston

How to Use Coffee Grounds for Garden Plants

Integrate Coffee Grounds into Compost

The best way to use coffee grounds for the greatest benefit to your plants, is to add them to your organic compost tumblers or compost bins along with other quality organic material. You’ll want no more than 25% grounds to food scraps ratio. A complementary balance of organic matter such as leaves, sawdust, grass clippings (but not grass that has gone to seed), helps in building a healthy compost pile.

This compost can be applied as you would normally use compost, such as soil for garden beds as well as amendments added during and/or after planting. Adding nitrogen fertilizer at the same time will encourage the growth of beneficial microbes.

Coffee grounds encourage the growth of soil microbes.

To Apply Coffee Grounds Directly Around Plants

Sprinkle coffee grounds loosely around plants, no more than 1/2″ thick. Avoid a dense layer as that can create a water barrier that redirects water flow away from your plant as well as diminished soil aeration and impact your soil microbiome. Alternately, you can work the grounds into the top inch of soil using a garden claw or trowel.

Coffee Grounds Tea

A coffee ground “tea” was recommended by one extension newsletter. However, this should only be applied to plants indicated as acidity friendly, because adding water to coffee grounds will result in a higher initial acidity due to the water soluble aspect.

Plants that may benefit from a tea are those well known to benefit from acidity.

How to Make Coffee Grounds Tea for Plants

To a 5 gallon bucket, add:

1. 2 cups of used coffee grounds
2. Steep for a few hours or overnight.
3. Use the mixture as a liquid fertilizer for the garden, yard, or container plants.

Apply With Caution, Experiment and Observe

Since caffeine, has been found to retard plant growth in some plants, so we highly recommend running your own test.

For example, if you have two of the same kind of plants, whether indoors or out, run your own experiment. Whether using coffee grounds, coffee grounds tea, or compost with coffee grounds, try the coffee grounds, tea or compost on one plant, but not the other. Otherwise, provide the same growing environment, watering schedule and nutrients, while observing if there’s any notable difference between the test plant/s (receiving the coffee treatment), and those not receiving it.

Similarly, for grass, test the coffee “tea” in a test area where you can easily identify and track any difference between where you’ve applied the tea and where you have not.

REFERENCE: University of Wyoming, Summer 2017 Newsletter, article by Lisa Ogden in Barnyards & Backyards^[15]http://www.uwyo.edu/barnbackyard/_files/documents/magazine/2017/summer/plantsperk0717.pdf

Where to Get Used Coffee Grounds?

If you don’t drink coffee, or, you have more plants than coffee grounds to go around, you may be able to get used coffee grounds for free. Check with your local coffee shop or Starbucks to see if they have a regular day for used coffee ground pick-up.

FAQs – About Using Coffee Grounds for Plants

Do Roses Like Coffee Grounds?

Not exactly.

But roses benefit from the soil microbes that like to munch on the fungi that like to attack the roots of roses and lead to wilt and rot.

So attract the soil microbes with spent coffee grounds and while they’re there, they will clean up the bad boy fungi like Fusarium, Pythium, and Sclerotinia that can attack your favorite rose bushes.

RELATED: we love growing knockout roses. Such lovely, hardy, carefree producers.

Sago Palms – Coffee Grounds for Sago Palms as Fertilizer and Pest Deterrent

Contributions from GardensAll Reader, Janine Morris, hobby gardener

I have experience with Sago palm and coffee grounds. Sago palm, which is not even a palm, is actually in the Cyad family. It loves coffee grounds for fertilizer and pest deterrent.

How to Apply Coffee Grounds to Sago Palms

• I collect the used grounds in a ziplock in the fridge for about 5 days.
• Then I put it in cake pans and let it dry in the sun.
• Once dry, I spread it directly on the soil around the sago palm.

I use coffee grounds near all of my palms, ferns, grasses and roses. Not as much as the sago gets though.  I usually mix it with Epsom salt for everything else.

Great to know! Thank you, Janine!

Coffee Grounds and Eggshells for Plants

Coffee Grounds and Eggshells

Contributed by “CoolCat”

I buy Starbucks Espresso Roast whole bean. I have 4 shots a day (Quad), saving my grounds in one bowl and egg shells in another. I mix them together, breaking the shells into really small pieces.

We have the DARKEST GREEN RYE grass I’ve EVER seen! I also planted 6 Plumbago bushes which are now 5 or 6 years old. The blue blooms are MORE VIVID than my plumbagos I grew in California! (I live in the hot, dry desert of Phoenix, Arizona now).

I have sweet peas who love the mix, and about a 4′ by 2′ strip of blue Aloe Vera who also love it. African Daisy’s love it too, along with some pretty whisky pink flowered bushes I planted with the hottest pink blossoms! When people see my backyard they classify it as a “haven.”

Clearly…something IS working!

Try it out! brown organic eggshells I am for, but I toss white shells in there, too!  

Good Luck!

Do Tomatoes Like Coffee Grounds

The pH of coffee grounds won’t make much of a difference for your tomato plants. However, the coffee grounds will appeal to the soil microbes that fend off the same fungus problems that affect roses. So blending in some coffee ground with your compost should help keep your soil hospitable to your tomato plants.

Will Coffee Grounds Get Rid of Ants?

Contributed by Doug Morissette

I have had a very good experience using coffee grounds in my greenhouse.

I had a severe ant infestation in my greenhouse three years ago. My greenhouse is 14’, 9” long by 7’, 9” wide, aluminum with tempered glass on a pressure treated wood base on top of crushed gravel and was installed in 2005.

The ants were eating away at the pressure treated wood, running everywhere in the greenhouse and nothing was getting rid of them.

I started to lightly cover the entire surface of the soil with coffee grounds to assist in moisture retention.

As I drank more coffee I kept storing the grounds in extra large Ziploc bags. When the bags were full I would take them out to continue covering the surface of the soil until I had finally covered all of the soil.

To my surprise after a week of putting the coffee grounds down I could not find a single ant in the greenhouse. I continue to sprinkle the coffee grounds and after three years there is still not a single ant in the greenhouse. The added bonus was that the annoying chickweed stopped growing in the greenhouse!

~Regards, Doug Morissette, gardener 

WOW! That’s an awesome tip to know. THANKS for sharing that, Doug!!!

Some Reasons for Confusion on Using Coffee for Plants

• Coffee is acidic
• But spent coffee grounds are considered more neutral than acid
• Some studies cited are studying coffee crop refuse in agriculture, which includes the coffee bean husks and fruit pulp and which varies in acidity as compared to coffee or coffee grounds.

Because coffee is known to be acidic, it’s easy to assume that coffee grounds are therefore also acidic for plants. However, as indicated above, the coffee grounds are only mildly acidic and trend to mildly alkaline over time.

Coffee is one of the world’s most popular beverages and the second most traded commodity after petroleum, ^[16]https://www.sciencedirect.com/science/article/abs/pii/S0921344912000894?via%3Dihub with more than two million tons of coffee residues, such as coffee pulp, husk, and grounds annually.^[17]https://www.sciencedirect.com/science/article/abs/pii/S0959652618336333?via%3Dihub

CONCLUSION on Using Coffee Grounds for Plants

We shall continue mixing our spent coffee grounds into our homemade organic compost. In the small percentages we’re mixing in, it’s not enough to disrupt the worm population, which remains healthy.

We will also set aside used coffee grounds to apply directly to areas where weeds are not welcome, and plan to conduct our own study of applied grounds in comparison to a control area without SCG for weeds.

While a lot of research has been done on the uses, benefits and deficits of using coffee grounds for plants, there’s still confusion on the subject.

The good news is that there is enough evidence of spent coffee ground (SCG) benefits, including the repurposing of massive coffee grounds to be put to good use instead of clogging landfills and caffeinating waterways, that we’re hopeful that research will reveal more of what’s possible for the refuse of this magic bean!

For other uses for used coffee grounds, check out this article on growing oyster mushrooms on used coffee grounds.

REFERENCES:

• University of Vermont Extension Department of Plant and Soil Science spring newsletter by Charlie Nardozzi, Senior Horticulturist, National Gardening Association
• Oregon State University article on coffee ground composting^[18]https://extension.oregonstate.edu/gardening/soil-compost/coffee-grounds-composting
• Field Evaluation of Coffee Grounds Application ^[19]https://www.tandfonline.com/doi/mlt/10.1626/pps.17.93
  • Summary
  • PDF
• University of Wyoming, Summer 2017 Newsletter, article by Lisa Ogden in Barnyards & Backyards^[20]http://www.uwyo.edu/barnbackyard/_files/documents/magazine/2017/summer/plantsperk0717.pdf
• University of Wyoming, summer 2017 newsletter, article by Lisa Ogden in Barnyards & Backyards
• Urban Forestry Study, Sarah J. Hardgrove, Stephen J. Livesley 2016

Our Favorite Coffee

We really like the organic Ruta Maya coffee. We used to order it through Amazon until we discovered it’s a couple dollars less per pounds (currently) for the 5 pound bag from Costco. Of course you have to calculate in shipping, but if you meet the minimum on an order, or pick it up in the store, then there’s no shipping charge.

Okay, whew! That’s a wrap! Please share with us your experience and observations on using coffee grounds for plants, and and how that’s working for you.