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I have a question about adding coffee grounds

Richland, WA(Zone 7b)

I am collecting coffee grounds from my local Starbucks, and will have plenty to share with friends by the time warm weather gets here. I am wondering if it is possible to add too much to my garden soil. What would possibly happen if I *overdosed* with the grounds? I know worms love them, and they help aerate and improve the texture of heavy soil. Any info will be welcomed. I sure don't want to do harm to my soil!

Provo, UT(Zone 5a)

i dont know what your soil profile in utah
ours is alkaline,i live in a river bottoms good drainage..
ive ammended soils here with ALOT of compost.. and continue
to add coffee grounds..
i even throw grounds on my does make it a bit bumpy,
because of the worms showing up..i rather have slight
bumpy lawn and the worms..:)
whats to much? i think it would take a WHOLE LOT of grounds
to be to much..again..depending on your soil profile..
there have been some good posters here..with actual university
studies on affect of coffee grounds.. its not as acidic as i think we
all thought..
im guessing..but i probably ammend my soils here with shy of 1000
lbs of coffee grounds every yr..
no im not shaking from the caffeine LOL.. i also collect from coffee joints..
i also add to my composts
good luck to ya !!!!!

Richland, WA(Zone 7b)

Thanks, tropicacalnut- that's just what I wanted to hear! I will keep on collecting- I get about a 5 gallon pail every day!

SE Houston (Hobby), TX(Zone 9a)

You can NEVER add too much coffee grinds. Go for it!!!

Odessa, FL(Zone 9b)

Have your Ph tested at your local Extension Service. If it is 6.5 or higher, pile on the coffee grounds. If it is 5.5 or below, back off a bit.


Madison, AL(Zone 7b)

You really can't OD with coffee grounds on any kind of drag-the-bags-home from the coffee shop scale.

I will say that if you layer them too deeply on top of the soil, it seems to impede water absorption from rain and increase run-off (when on a slope.) Also seeds don't seem to want to sprout if there are too many grounds right up next to them, which I suspect is just the clumpy texture and large grains of the grounds.

Richland, WA(Zone 7b)

I am so encouraged- it will get well tilled into the soil with my little B&D 18v cultivator. It is such fun to use it's like playing! A neighbor is bringing me 2 50gal drums today, so I can really stash the grounds!

Everett, WA(Zone 8a)

Hmm, if you have vast amounts of coffee grounds, you could have 2-3 times as much compost! Coffee grounds have a high nitrogen content and they are already finely ground.

You could add 2-3 times as much sawdust or shredded paper to you coffee grounds heap, and it should compost pretty fast. Then spread and till in the compost for even more organic benefit.

Or just lay 3-6 inches of paper or cardboard under your coffee grounds pile. That will absorb some of the nitrogen that leaches out over the winter, and compost itself. Old phone books with covers torn off? Stacks of newspapers?

Richland, WA(Zone 7b)

It sounds like I just struck gold! I hope there are others saving from Starbuck's- it's unbelievable how many of those pods they use every day! (I don't even drink coffee!) If every one was about $4-- that's a LOT of $$$

Everett, WA(Zone 8a)

Around half of local Starbucks have the "Grounds for Gardeners" bucket. The rest have them picked up by commercial composters (Cedar Grove Compost).

However, 99% of the time, the five-pound bags of grounds were grabbed by gardeners faster than I am!

I found one place that was slow to bag their grounds. If I got there at the right time with a very sturdy plastic bag, they would tip the big rubbish can full of used grounds into my big bag. That was easier for them than shoveling wet grounds into 5 pound bags and taping them up.

But I had to come in at just the right time: the can had to be light enough to tip, but full enough to be worth their while. And the counter people had to be not very busy.

Richland, WA(Zone 7b)

I am on a ROLL! Today I scored a source of 55 gallon whute plastic drums from a neighbor who runs a carwash- they are eco-friendly- I cut them around the middle, and will store the coffee grounds in them until spring, then I will drill holes around the sides, and they will be potato buckets. I am going to get 3 more and will plant lots of things in them.

Thumbnail by JoParrott Thumbnail by JoParrott
Everett, WA(Zone 8a)

Nice score!

If half-a-drum is deeper than you need for a container, you might cut an 8-16" slice out of the middle, and use that to make a second tier on top of an existing raised bed. Trailing plants could go on the top layer.

Richland, WA(Zone 7b)

RickCorey, you are a wealth of ideas- you could be a *yankee*,(like me!) I am always improvisingand re-purposing stuff.

Helena, MT

Jo, would like to add another thought to our friends great ideas, something which I think will be more popular in the future...outdoor vermicomposting. You can take whatever organic materials are available to you for composting, layer them like lasagna gardening up to three feet deep, and add some compost worms. It may take some time to completely break down on its own, but occasionally turning the pile(s) and watering will expedite the process. The worms can increase the benefits of composting by as much as four or five times. Other advantages include cutting down on weed seeds in cow or horse manure, and reducing the ammonia content in fresh manures which may burn crops.

I built a 1/4" screening device with 1" x 4" boards a few years ago which fits over my wheel barrel. Once the vermicompost is broken down it just takes a couple of minutes to screen the vermicompost and then shovel it into the garden row, till with my Mantis tiller, then plant. The vermicompost is no wasted on the rows which makes it go even further.

Maybe I will call this process Lasagna Vermicomposting.

Richland, WA(Zone 7b)

Thanks, mraider- maybe I will try that. I really don't have any space to devote to it, but will try to find a little corner. I also made a 1/4" screen sifter that goes over my wheelbarrow! If the weather ever gets better I will get a photo of it. Great minds do think alike! A few years ago I was reading about vermicomposting, and there was something about what kind of worms to get and what not to use. Any input there? I did buy worms and add to my garden, but I don't know what they did! I see an occasional one, but not nearly what I would like. The 3 half barrels I planted potatoes in were heavy with worms last year. I had put a layer of leaves in the bottom of each, and when I dumped the soil out to freshen it up, there were thousands of worms of all sizes.

Charlotte, NC(Zone 7b)

I don't know what kind of earthworms we have, but we throw our kitchen scraps into a compost bin, and in the spring there are literally millions of earthworms.

When we first moved here, I had to go into the near-by woods to hunt for earthworms - I found four!

Madison, AL(Zone 7b)

Quote from JoParrott :
Thanks, mraider- maybe I will try that. I really don't have any space to devote to it, but will try to find a little corner. I also made a 1/4" screen sifter that goes over my wheelbarrow! If the weather ever gets better I will get a photo of it. Great minds do think alike! A few years ago I was reading about vermicomposting, and there was something about what kind of worms to get and what not to use. Any input there? I did buy worms and add to my garden, but I don't know what they did! I see an occasional one, but not nearly what I would like. The 3 half barrels I planted potatoes in were heavy with worms last year. I had put a layer of leaves in the bottom of each, and when I dumped the soil out to freshen it up, there were thousands of worms of all sizes.

Most of the worms you can buy in bulk are red wigglers (Eisenia fetida). They aren't really suitable for outdoor or general garden worms in our zone; they are surface dwelling worms and can't tolerate our winters but also can't dive deep into the soil to stay warm. (Although some of their egg casings may survive.) For indoor bins, red wigglers are the champs of the vermicomposting world. For outdoors, your best bet is to attract local worms. If you are composting, you can bet worms work your compost!

In our zone, earthworms are mostly active in the spring and fall so if you do most of your digging in the summer you may not see many. A layer of rotting leaves put down in the fall is a great way to get them to work your garden and have lots of babies. A few years ago I hardly had any, but mulching and incorporating leaf compost has brought my population up from almost none to scads of them (despite the "help" from the robins). I get it by the truckload from the city at no charge -- but I have to haul it myself. You may have a similar program in your area.

Helena, MT

Nicole, most people think outdoor vermicomposting is done with garden worms but that only works if your composting is done below ground. Garden worms in an above ground vermicompost operation are burrowing worms and stay near the ground level, while the leaf worm or red wiggler will typically be found in abundance in the upper layers. If you have an outdoor compost pile up to three feet tall you can introduce red wigglers and they are much more efficient in breaking down the organic matter than garden worms. If the pile is more than three feet tall the worms will not be found in the lower layers due to a lack of oxygen. Turning otherwise static piles with red wigglers as often as twice a week and watering helps speed the process. If you want to start a new pile give it about a week and take the top ten inches off the old pile and add to the new.

As far as using red wigglers in the garden goes I would have to disagree with the theory that it's not possible. I have gardened in northern Montana for ten years and not until last season have I ever seen a single worm other than the red wigglers which I add to the holes dug for squash, cucumbers, peppers and tomatoes. Some how a few even survive the winter in these holes which surprises me. But they do a good surrogate job of aerating the soil in place of the common garden worm which I am now seeing along with a pinkish grey nightcrawler, and some Canadian and European nightcrawlers which I had introduce after fishing trips.

Our frost lines can go down as much as 18 inches or more where we hit bed rock and if it wasn't for all the organic matter I have added over the years I doubt there would be much of a survival rate for any type of worm. With the build up of organic matter over the years my garden seems to be generating sufficient heat in the winter months to allow the worms to survive. Snow cover melts much faster and there isn't any build up like in my yard.

Everett, WA(Zone 8a)

Thanks, JoParrot! I hate to throw anything away, so I feel ob liged to imagine ways in which I might use things.

I friend had a circular many-tier raised bed that looked like a wedding cake or a circular Mayan pyramid.

He had some kind of metal edging that was tall enough that each step was raised 3-4 inches. Each step was around 6-8 wide. It was quite a few feet around at the base, but the top was just 12" in diameter.

Madison, AL(Zone 7b)

Hey Helen,

I'm glad you had success outdoors. I had dead worms as soon as it got truly cold -- which is still much warmer that your area in the winter. We've had the same experience with educational bins in the area. Some new worms always hatch out when it warms up, but the old ones die off in the first hard freeze. Eisenia fetida adults start dying at 45F and are usually all dead at 40F. Perhaps you are running a hot compost pile and that is providing enough warmth to keep them going? Or you are seeing young worm hatching from cocoons? E. fetida cocoons have an "antifreeze" mechanism under the right conditions that is pretty fascinating when the temp drops below 30F.

Charlotte, NC(Zone 7b)

Here are a couple of links about earthworms

Richland, WA(Zone 7b)

I have been reading about the effects of adding coffee grounds to the garden--All agree that you can't overdo it, but some sources say that if adding heavily you need to add nitrogen(see this article) Any opinions here? Would Blood Meal be good? or Cottonseed Meal?

Madison, AL(Zone 7b)

Thanks for the link - -there's some food for thought there.

How much coffee grounds are we talking about? I can bring home a 30 pound bag and it just doesn't go very far scattered on top of the soil. I can bring home TEN 30 pound bags and it still doesn't go very far. In the links on that page they discuss problems using 25% coffee grounds as potting soil and composting only with coffee grounds and newspaper and a bit more greens. I can see why that would be problematic -- you wouldn't use 25% uncomposted manure as a growing medium either. But I don't think that's on the scale that most gardeners use coffee grounds. I know I for one will never get anywhere near that kind of ratio of uncomposted grounds to dirt.

On the subject of nitrogen fertilizers, I use cottonseed meal lightly applied about 2-3 times per year. It's local and very cheap here in cotton country, sold by the 50 pound sack at the feed store, and about 6% nitrogen. Bloodmeal is about 14% nitrogen, but 40x the cost here. Bone meal, corn gluten meal, and soybean meal are other options; I would go with what is cost effective for your region.

Richland, WA(Zone 7b)

Thanks so much, Nicole- I pick up about 1 5gallon pail every day, and I sift it because most of them are pods that look like horse poop! So far I have added 8 pails to my 5x10' community garden, and 6 to my back yard garden that is 3'x60' long. I have also added a lot of ground up crab shells to my back yard garden. I think I will use Cottonseed meal on your suggestion.

Monte Vista, CO(Zone 4a)

I think I'd rather go with bone meal or something (chicken litter composted perhaps) instead of cottonseed meal, due to all the pesticides used on cotton, usually. I don't eat things that contain cottonseed oil, either, for the same reason.

Everett, WA(Zone 8a)

I've always thought that coffee grounds were one of the most nitrogen RICH things I put in my compost heap. I never heard they caused a nitrogen deficit. I could be wrong.

I think you could use 2-3 times as much in the community garden, or 10 times as much at home. I assume you are scratching it into the soil, at least enough that it doesn't form an impenetrable layer on top.

I bet the worms love you!

8 pails = 40 gallons = 5.3 cubic feet
5.3 cubic feet of grounds / 50 sq foot community garden = 1.3 inches deep layer of coffee grounds

6 pails spread over 3'x60' = 4 cu ft / 180 sq ft ~= 1/4 inch deep

Madison, AL(Zone 7b)

Jo, 8 pails in 80 square feet does seem like a lot of grounds. I'd love some ground-up crab shells but the only crabs I see are frozen in the grocery store. :) I'm leery of tossing the leftovers from our occasional crab dinner on the compost pile... who knows what it'd attract.

Solace, I had similar concerns with cottonseed meal so I did some research before I bought any. Cotton growing is nowhere near as bad as it used to be chemical-wise, but it's still pretty thoroughly sprayed for weevils before the boll opens up and then defoliated before harvest. I looked up some independent lab test results and there's really no significant levels of contaminants left in the dry cottonseed meal they sell or on the cotton itself. Sorry I don't have links since it's been a while, but as I recall the only truly independent tests I would find were European labs testing US and Mexican cotton.

I only use about 15 pounds a year, and I would guess a whole lot worse washes down the hill from peoples' lawns and ends up in my garden. While it's in my comfort zone, I know it's not in everyone's. I've seen bags of meal advertised as low-pesticide, but I don't know that there's any kind of specific limit to get that label? It might be a marketing gimmick. It's something to consider investigating is residues are a concern to a particular gardener. Organic cottonseed meal is available, too.

The same can't be said for cotton gin trash or cottonseed hulls -- I wouldn't touch that stuff.

Unfortunately, soy and corn are also very chemically intensive crops, which are the other two major plant-based nitrogen fertilizer byproducts. I am doubtful they would be any less contaminated.

Ideally we'd all have such perfect cover cropping and rotation schemes, we wouldn't need to add any nitrogen... but I'm not there just yet!

This message was edited Jan 31, 2013 2:19 PM

Richland, WA(Zone 7b)

It's beginning to sound like I just go for it and see what happens! I try not to overthink things, anyway. But reading that the coffee grounds could steal nitrogen concerned me a little- but not too much! I refuse to get too scientific about anything, so time will tell if I did the right thing. I do like reading that a layer of grounds will deter slugs- I don't have e real problem but any help is welcomed! My crab shells were ground up in an old VitaMix container that I use just for compost making-- I had bought 16 Dungeness crabs last month when the season was on! I have lots in my freezer now, all vacuum packed and ready to enjoy later.

Everett, WA(Zone 8a)

I found a few sources that mention that used coffee grounds add nitrogen to a compost heap. They're about as rich as green grass clippings. I didn't find any dissenting opinions in the first page of Google results.

"The grounds are relatively rich in nitrogen, "
"About 2 percent nitrogen by volume, used coffee grounds can be a safe substitute for nitrogen-rich manure in the compost pile, explained Cindy Wise, coordinator of the compost specialist program at the Lane County office of the Oregon State University Extension Service."
"First of all coffee grounds are a very good addition to your composting efforts. They would be considered a "green" or nitrogen source. C/N ratio about 20:1. "
Coffee grounds are another source of nitrogen for the compost pile; they have a carbon to nitrogen ratio of 20-to-1, equal to that of grass trimmings (see References 1).
Washington State University; Backyard Composting; Bob Smith; 1995
"Coffee grounds have a carbon-to-nitrogen ratio of 20:1, roughly equivalent to that of grass clippings. After brewing, coffee grounds contain up to 2% nitrogen. For composting purposes, consider coffee grounds "green" material similar to grass clippings. ",default,pg.html

Richland, WA(Zone 7b)

Rick, thanks for your time in quoting those items. I think I will just forget about any extra nitrogen--- did you read from the link I included? I wonder how they arrived-oh well, I will do my thing and pray!

Liberty Hill, TX(Zone 8a)

I thought coffee grounds added Nitrogen.

Richland, WA(Zone 7b)

lisa, there are conflicting opinions about that, but I am not going to worry about it- I will use it and see what happens.

Helena, MT

My coffee grounds go directly into my indoor vermicompost bins. Seem to be a favorite food of the worms. Studies I've read indicate coffee grounds have about 5% nitrogen, however vermicomposting coffee grounds should increase their value several times over simply adding them directly to the garden. Recent studies are indicating Vermicompost is 4 or 5 times more effective than composting without compost worms.

SE Houston (Hobby), TX(Zone 9a)

How much coffee grinds are you adding to your bin(s) and how often?


Helena, MT

Whatever I have available Linda, and whenever I feed which is usually not enough. Both wife and I drink coffee but I could always use more, and I don't think there is any risk with over applying coffee grounds. Although it is difficult to tell once the grounds are mixed into the media I have never seen any evidence of residual coffee grounds fed to my worms. With the number of worms in each of my bins they will more than likely consume the coffee grounds in a single day.

I am going to solicit some of our small coffee shops to see if they will save me their coffee grounds. A good experiment to try would be to spread the grounds about an inch deep in the feeding trenches and see how long it would take before the grounds were processed.


SE Houston (Hobby), TX(Zone 9a)


Everett, WA(Zone 8a)


A 7-11 may produce more grounds than small fancy coffee shops. Maybe offer them some veggies or flowers in trade ...

Someone said that a shop is more likely to save you grounds if you give them clean buckets to dump into, and promise to come every day at the same time. Maybe make clear that you'll take away grounds AND filters.

P.S. to composters. One fruit stand said I could scavenge their dumpster for scraps. There were often many things that were not too rotten, smelly or drippy, like cabbage leaves.

SE Houston (Hobby), TX(Zone 9a)


Everett, WA(Zone 8a)

>> did you read from the link I included?

Yes, but it didn't make sense to me, either the
or the GrassRoots Garden or the OSU extension service.


Everyone agrees that coffee grounds have around 2% N, which is really high. Like green grass clippings and manure. How can adding to the soil, something really HIGH in N, cause a N deficit?

They say it encourages microbial growth. To make sense of that causing a N deficit, it can't be a direct result of breaking down the grounds, because that would release relatively MORE N than it releases C.

It would have to encourage such a HIGH amount of growth that they suck down even more N than the grounds provided. Or so0mehow encourage the growth BEFORE the grounds broke down.

Speculating, it might improve the aeration so much that soil with lots of C and already too little N, and not enough oxygen, was suddenly opened up and burst into growth so rapid that microbes consumed other C faster than they could break down the (N-rich) coffee grounds.

(Speculating facetiously, maybe residual caffeine leaches out instantly and STIMULATES a caffeine buzz in existing microbes. The hyper-active little buggers now steal N from plant roots as they metabolize existing organics even before the coffee grounds decompose at all.)

But that's pure speculation. Basically, I'm a little skeptical about accepting something until I understand HOW it could be true. I can't say that invalidates the claim that your link quoted. I'm just hesitant to accept it until I understand how it COULD be true.

It doesn't affect how I garden: I never have lots of grounds. I use them more like a spice than an ingredient, trying to attract worms. I put them into compost m ore often than soil anyway. And all my beds are so low in N (and organic matter) that I continuously fertilize at a low level to supplement the pathetic soil I'm gradually enriching.

For someone adding grounds to rich, fertile (high-N) soil, sucking up some N temporarily is a non-problem. The N is already there, available to be used. If plants spent a few days or a week with "enough" N instead of "plenty" of N, they slow down little if at all. If N was not already limiting their growth, zero problem.

If there is a temporary N-deficit from coffee grounds, and a long term contribution of N and C, I'm happy as a clam (or happy as a worm). I'll continue to add small amounts of chemical fertilizer and whatever few coffee grounds I can get my hands on.

For others, I suppose it makes sense to compost ANY high-N stuff before adding to soil. You can double or triple the amount of organic matter that way, by adding as much sawdust or shredded paper or dry leaves, as you add coffee grounds.

Thanks for making me aware of this seeming paradox!

Helena, MT

Corey, I lost track of this thread after reading the link you posted on coffee grounds. Thought this was posted in another forum.

Two thinks struck me about this article. The comment of coffee grounds making the soil acetic was new to me. I had never heard that before and I have to agree with the author on that assumption. As for adding coffee grounds directly to the garden I also agree with his assessment. You get far more benefits from coffee ground if you process them through vermicomposting first.But like you Corey, the authors comment about microbes taking up more nitrogen than the plants doesn’t make any sense to me.

One of the most interesting uses of coffee grounds was from a DGer who said she collected coffee grounds from coffee shops and spread them on her lawn with good success wherever she applied the grounds,

As for attracting worms I think there is some confusion here. The common garden earthworms are burrowing worms and will obviously be attracted to coffee grounds incorporated in the garden. However, if you are planning on garden earth worms to come to your vermicompost piles forget it. The worms used to vermicompost are generally found in old leaf piles and not the burrowing type. These babies are the real work horses in indoor and outdoor vermicomposting. However, seeding these leaf worms is necessary to get a good jump start in outdoor vermicomposting . I seed thousands of my indoor compost worms into my raised beds and garden each year where they do a great job of aerating the soil.

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