At a certain point I might as well admit that we drink a rather obscene amount of coffee. It’s almost all frugal, brew-at-home type coffee, but still: that stuff ads up.
Luckily, the grounds are almost as valuable as the liquid coffee, and we save them for use in the garden, thereby getting the most bang for our fair-trade-coffee-buck.
These are my five favorite ways to use coffee grounds in the garden.
Sheet Mulch
The majority of our grounds get dumped out, directly on the soil, as sheet mulch around around our berries and fruit trees. The common assumption is that coffee grounds are acidic, but tests on the pH of grounds have shown results from mildly acid to mildly alkaline, and research indicates that the pH of the grounds tends towards neutral as it decomposes. I use coffee grounds as a mulch around blueberries, fruit trees, currants and cane fruit, all with good result.
When you mulch with coffee grounds, don’t pile it on. That’s a sure-fire way to get moldy mulch. A good half-inch thick layer atop your normal organic mulch in any one spot will do nicely. It will break down relatively quickly as worms and soil microbes go to work, and when it does you can add more. Coffee works like any other organic mulch, with a few added advantages discussed below.
Side-dressing for Heavy Feeders
You probably know that the main nitrogen component in DIY organic fertilizers, like Steve Solomon’s famous mix, is seedmeal. Well, if you think about it, a coffee bean is a processed seed. As you’d expect, coffee grounds are high in nitrogen, at about 10%. Depending on the exact beans and extraction process, “the carbon to nitrogen ratio of coffee grounds can be as low as 11:1, an ideal ratio for plant and soil nutrition,” according to WSU extension.
With nitrogen levels like that, pure coffee grounds make an excellent side-dressing for leafy greens and hungry fruiting veg, like tomatoes and squash, early in their growth. I particularly like side dressing spinach with used coffee grounds.
Natural Slug Deterrent
Slugs get the heebie-jeebies crawling over coffee grounds. I think it scratches their slimy underbellies in an unpleasant way. Do you have some veg, like Napa Cabbage, that seems like a total slug magnet? Try banding coffee grounds in a uniform circle around the plant as a seedling, and keep the band topped up. It helps. I’m not giving away my Sluggo just yet, but it helps.
Vermicomposting
I know some people say that you shouldn’t feed worms coffee grounds, but I have Seattle worms. They’re all holding teeny Starbucks cups and wearing fleece vests as they crawl around their worm bin, talking about Python hacks and when they’ll finally be able to get up to the mountains to go snowboarding.
Coffee grounds aren’t the only thing I put in my worm bin, of course, but mixed in as part of a balanced diet of cardboard, shredded paper, kitchen scraps, banana peels and the like, the worms seem to process coffee grounds without any issue.
Suppression of Fungal Diseases
Decomposing coffee grounds have their own fungal and mold colonies and those fungal colonies tend to fight off other fungal colonies. If this seems weird, just remember that the antibiotic penicillin was developed from a mold. The world of teeny, tiny things is fighting for space and resources just as fiercely as the world of big, visible things, and you can use that to your advantage.
The natural mold and fungus colonies on coffee “appear to suppress some common fungal rots and wilts, including Fusarium, Pythium, and Sclerotinia species,” according to research. It’s hard to quantify exactly how this all plays out in the big outside world with millions of variables, but incorporating coffee grounds into your compost may help to prevent build-up of nasty verticulum and fusarium wilt inoculates. I figure it’s worth a shot. If I have coffee grounds on hand, I will throw a handful of grounds into the transplant hole for tomatoes, peppers or eggplant, since these plants tend to be susceptable to various wilts.
How do you use coffee grounds in your garden?
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Using coffee grounds as a seed meal? Wow now this is something innovative for me. I must tell that my family consumes a hell lot of coffee and I think for them this idea is surely gonna work. Thanks for sharing this wonderful piece of information, my garden will be always thankful 🙂
My wife and I collect grounds from the local coffee kiosk year around. We don’t make a special trip, but when we stop for a “fix” we depart with whatever ground they have. In the spring and summer there’s competition for the grounds, but in the winter I must be the only one collecting cause there’s always 50-60 pound waiting by the door. I stack it by our compost pile and it freezes into a block wall. Seeing how tall is a game I play. On the spring we start spreading it on our hems, asparagus, fruit trees… It’s sometimes moldy and caked, but we smash it up and use it. Haven’t noticed any problems from the mold. Like I read at the beginning of this article, it might be beneficial? !
So, what about mulching a potted Sweetcrisp Blueberry bush? Lately I’ve been emptying out my coffee maker on the bush. I’d simply remove the filter (w/ used grounds) and turn the filter upside down on the soil’s surface. Any thought?
Wonder if this would help keep the stray cats from using my mulch as their litter box?
I was reading about the tobacco soak for aphids. I had a ton of aphids on my broccoli and brussel sprouts last year. Is someone able to tell me the recipe cause I would try it this year. Love reading all the posts!
Just break up a cigar in to a jar of water and let it soak a few days. Then dilute it 10;1 and apply with spray bottle. Make sure the cigar has no additives, like scents for example. You want tobacco only, that is processed as little as possible!
Do not use coffee grounds in your garden if you have dogs, it is toxic to them
Plant one clove of garlic between each rose bush ( in December ideally but anytime will deliver benefits ) and you won’t see a single aphid on them. Then harvest the garlic for use in the kitchen – warning – it’ll be stronger than anything you buy in the shops
No kidding? I get aphids like crazy any time I try to grow basil outside. I wonder if garlic would help there.
Besides tossing the coffee grounds in the compost bin, right about this time of year I lay a pretty sizable amount on one of my hydrangeas to produce an ombre-effect in the blooms. I confine this “science experiment” to just the one plant and get rave reviews on the lovely colors.
I knew you could use coffee grounds in the garden but wasn’t sure what it actually did. I’m psyched to hear it will benefit my fruit trees. I have four. Also…Seattle worms…very funny.
Absolutely pointless, they did absolutely nothing for my garden and I am extremely disappointed.
I use coffee grounds in my potted plants to deter chipmunks. The little guys love to dig in my pots unless I put coffee grounds on top of the soil. For some reason, the grounds seem to keep them out.
About a month after sprinkling my used coffee grounds around my strawberry patch, they have gone absolutely mad with growth and runners. I’m a believer.,
Hi,
I am so late to reading this but have been using grounds on my tomatoes for years. What I don’t know is – how safe it is for me to use grounds on fuschias and flowers in hanging planters? How bout primroses, pansies and others?
I just picked up grounds from Starbucks and was wondering how best to use them. Discovered your site when I did a Google search. Thank you and those that commented for some wonderful information.
As a follow up on the neutral acidity of coffee grinds report here is information published later.
For a full read of the reply to the question on acidity:
http://www.gardensalive.com/article.asp?ai=793
Here is a portion of the reply.
But then we were sent some test results that showed grounds to be neutral on the pH scale! To find out what gives, I called Will Brinton, founder and Director of the Wood’s End Research Laboratory in Maine, the definitive testers of soils, composts, and raw ingredients used in large-scale composting. Will solved the mystery instantly. Woods End, it turned out, was the source of that neutral test! Ah, but some follow-up investigation later revealed that it hadn’t been coffee grounds alone, as the person submitting the material for testing had stated, but grounds mixed with raw yard waste, the classic ‘dry brown’ material that is the heart of a good compost pile.
It turns out, as expected, that “coffee grounds alone are highly acidic,” says Will, who saved all the grounds from his Lab’s break room for a week recently just to test for us (“Eight o’ Clock” coffee, which I remember fondly from our old A & P neighborhood supermarket). They came out at 5.1, a perfect low-end pH for plants like blueberries that thrive in very acidic soil. “But that’s the most gentle result we’ve ever found,” Will quickly added, explaining that the other 31 samples of raw coffee grounds they’ve tested over the years all had a pH below 5, too acidic for even some of the so-called acid loving plants.
“And in some ways, the grounds are even more acidic than those numbers imply”, adds Will, who explains that the coffee grounds they’ve tested have also had a very high residual acidity; so high he recommends adding a cup of agricultural lime to every ten pounds of grounds BEFORE you add them to your compost pile. (High-quality hardwood ashes could be used instead of the lime, and would add more nutrients to the mix than the lime would.)
I am new to all of these ideas, but I am so grateful that there are sites like this one that I can learn new and exciting ways to help my rise garden. Thank you so very much.
I have a couple of feet of dirt between my patio and fence. I plan on digging deep holes with a post
hole digger and dropping in a fish some bone meal and coffee grinds. Then covering it up and watering it with fish emulsion and seaweed emulsion and covering it lightly with mulch till planting time. Is there anything else I should drop in the hole?
Don’t make the hole too deep unless what you plan to plant is known for deep roots… shrubs and most herbaceous plants don’t root all that deeply. Putting fertilizer three feet down won’t do much for surface stuff until the worm activity turns it over, and that takes years.
Hello,
Now that I have completed radiation & am moving into a new home to establish new raised beds I am intrigued with the used coffee grounds idea for my new beds & compost. I will soon be back to baking, using lots of eggs—I use the shells, (crumpled in my hands), around the “slug vulnerable” plants & also in my outside large, potted, plants.
I grew up where gardening was a way of life & love that so many are trying it. Good for all of us! I so missed gardening while not feeling well but it was beyond me. Now to learn what I can about the Knoxville,TN climate & winters.
Way to go everybody!
Hello,
I have so enjoyed reading the vast range of used coffee grounps.
I have been sprinkling coffee grounds (yes, also scraping them out of the K-cups) along the house foundation right on top of the mulch. I read that a line of coffee grounds will deter ants from entering your home. Seems to be working. We had quite a few ants in the kitchen before I started doing this.
Erica, spot on, this topic of coffee grounds. So much so, I referenced my new blog to this Awesome blog by you.
Thank-you for sharing you’re passion with others.
Cheers!
I saw a little tips site recently to do with lemons that recommended mixing lemon peels with coffee grounds to keep dogs and cats away from gardens. Is this accurate? I don’t want to hurt anyone’s pets, but I like the idea of them not using my garden or my containers as their litter box. I don’t drink coffee and it’s the whole reason for me to pick up spare grounds in the first place. Would I be hurting animals or my plants and garden ground by adding the coffee grounds and lemon peels?
I used coffee grounds to get rid of ant hills in my garden. Only used it once and the ants haven’t come back.
Coffee grounds….used, of course, are a summertime process. I save about 4 cups in a saved container, and when full, add a handful to an ice cream pail of water, mix it by hand, and water in at the base of each flowering plant. When empty, repeat. My peppers were better sized than store bought, tomatoes all overproduced, and so did beans, peas, carrots and cucumbers. As for roses, there are no bugs on the rosebuds, and the other flowers grew healthier. One other thing: deer and rabbits don’t like the smell of it, so I had full rows of undisturbed plants all through the growing season.
In 2015, I did this twice, but also have been using Epsom salts at the base of each plant, once or twice a growing season. The flavors are sweeter, it’s chemical name, magnesium sulphate, is great for plants, and the tomatoes do not have blossom end rot. It’s sold by greenhouses and stores every spring, and makes a cheap fertilizer.
Very much enjoyed your treatise on composting with/by chickens,, and read it through, even though I live in the middle of a Central Ontario city with 65000 inhabitants. Its by-laws prohibit livestock of any kind within its boundaries. I’m keeping the advice because I own a 60-acre “gentleman’s hobby farm” 160 miles away in Eastern Ontario, to which I expect to retire in a bout a year.
Thanks for posting your hands-on knowledge!
If you look on line there are a ton of videos showing honey bees being attracted to coffee grounds – including my caffeinated bees video.
This is especially noticable in the winter when there is no pollen or nectar to return. It was in the 70s this winter and the bees will take flight to “evacuate”. You will get yellow poop spots on your vehicle on the first warm, calm, day after a spell of bad weather.
No one seem to know what attracts them. They seem to be taking granules back to the colony.
Post this if you want.
Composting worms need grit in their diet to process foods so coffee grounds are good and necessary for them
Great post. Thank you for the information. I am placing them around my basil and lettuce. Hmmm coffee basil. Wouldn’t that be interesting. Too bad it does not take on the taste.
I like your tips. I came to your web site by chance as I want to start fermenting food. I wanted info on how to use mason jars that I have at home. I cannot spend too much on buying equipment. Thanks.
This blog was… how do you say it? Relevant!! Finally I’ve found something which helped me.
Many thanks!
Hi, can I add used decaf coffee grounds around my 1st year lime bush about a foot high and do I need to prune tree if 4 or five lines are in a bunch close together
Thanks,
Don