coffee grounds

reaconJune 10, 2014

should coffee grounds be wet or dry before adding to your garden.


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seysonn(8a WA/HZ 1)

It will get wet once mixed in anyway. So it does not matter how you add it. JMO.

    Bookmark   June 10, 2014 at 9:09AM
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I would imagine it wouldn't matter like seysonn said. But do you use the grounds after made a pot of coffee with it? What it the purpose? Sorry for jumping on your question thread

    Bookmark   June 10, 2014 at 9:35AM
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seysonn(8a WA/HZ 1)

mfran ,
Yes . Coffee ground means what is left after brewing. You can use your own and/or get it for free from coffee shops.

    Bookmark   June 10, 2014 at 9:54AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

As to the purpose - it is one of those trendy fad claims floating around the internet. Some claim it adds nitrogen for the plant and some think they will help acidify the soil.

Research has proven to be invalid as the grounds after brewing contain very little nitrogen and their pH is almost a neutral 7.

They can be a very beneficial addition to compost piles but have only minimal benefit when added, without composting, directly to the soil.


    Bookmark   June 10, 2014 at 10:15AM
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johns.coastal.patio(USDA 10b, Sunset 24)

Based on a NPK analysis for coffee grounds from the North Carolina State University, the ratio is 2.1:0.3:0.3. Those figures can vary slightly, but it’s clear that ground coffee is nitrogen heavy.

2.1 might be low for a "fertilizer" but it's high for a mulch (or a compost) isn't it?

Ah, reported elsewhere: Homemade Compost NPK= Nitrogen 0.5% Phos 0.27% Potassium 0.87%

So, quad-strength compost.

Or, a pound of coffee grounds (2.1:0.3:0.3) will give you as much nutrients as an ounce of 35-5-5

    Bookmark   June 10, 2014 at 11:52AM
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seysonn(8a WA/HZ 1)

Based on a NPK analysis for coffee grounds from the North Carolina State University, the ratio is 2.1:0.3:0.3. Those figures can vary slightly, but it’s clear that ground coffee is nitrogen heavy.
Interesting .

John, that is more potent than most GOOD cow manures that they dare to put the analysis on the bags. As you mentioned it is not a fertilizer but it certainly can be used as top dressing like compost.
Beside its nutrients, I think it is a good soil conditioner and in small quantities, needs not to be composted first. One of the drawback of composting is that some of the Nitrogen can be lost in the process, IF not done exactly right.

    Bookmark   June 10, 2014 at 12:04PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Can't find that original source John, only a secondary quote from it on another site called Ground to Ground with it's own agenda. Apparently the original study he links no longer exists on the NC Ext. website. Do you have a link to the original study? I'd like to read it in context.

Per Science Daily

2 percent nitrogen by volume so while large volumes can supply beneficial levels of nitrogen, it is only available to the plant after it decomposes.

Contrary to popular belief, coffee grounds are not acidic. After brewing, the grounds are close to pH neutral, between 6.5 and 6.8. The acid in the beans is mostly water-soluble, so it leaches into the coffee we drink.

Mix grounds into soil as an amendment. Make sure to keep them damp. Add some nitrogen fertilizer if you do this, as coffee grounds encourage the growth of microbes in the soil, which use up nitrogen. While microbes are breaking down the grounds, the nitrogen will provide a source of nutrients for your plants.
Spread grounds on the soil surface, then cover them with leaves or bark mulch.

Keep in mind that uncomposted coffee grounds are NOT a nitrogen fertilizer. Coffee grounds have a carbon-to-nitrogen ration of about 20 to 1, in the same range as animal manure. Germination tests in Eugene showed that uncomposted coffee grounds, added to soil as about one-fourth the volume, showed poor germination and stunted growth in lettuce seed. Therefore, they need to be composted before using near plants

Coffee grounds also can be added directly to soil but the grounds need a few months to break down, Wise said.

From University of Illinois Extension

There is a lot of research-based information available on using coffee grounds in the garden. Research has shown that coffee grounds are about 2% nitrogen by volume, making them a great source of nitrogen for composting. Coffee grounds have been suggested as a safer alternative than using manure in compost piles.

Some sources will declare that because coffee grounds contain nitrogen, a major plant nutrient, this makes coffee grounds a great fertilizer. But just because they contain nitrogen, it does not mean that coffee grounds are suitable for use as a fertilizer as is. Some studies have shown that using uncomposted coffee grounds in high concentrations around plants will actually stunt their growth. The grounds need to break down before they are truly a benefit to plants.

While coffee grounds have been shown to have a nearly neutral pH around 6.5- 6.8 (neutral is 7), coffee reportedly has a pH of anywhere from 5.2 to 6.9 depending on the type of coffee and how it is prepared. The lower the pH, the more acid, and a drop in one full pH unit is equal to a factor of 10. So if brewed coffee is a pH of 5.5 and the grounds are 6.5, the brewed coffee is 10 times as acidic as the grounds.

For me the evidence supports composting them rather than adding them directly to the soil unless they are added in large volume to provide sufficient N but at the same time risk stunting the plant growth.

Draw your own conclusions.


    Bookmark   June 10, 2014 at 12:50PM
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johns.coastal.patio(USDA 10b, Sunset 24)

You are right that the "grounds to grounds" link dead-ends, but there are similar numbers at NPK of Organic Materials

I think we actually agree on what UCGs "are." They certainly are not concentrated fertilizer. Perhaps that's a redundant thing to say, because it is the concentration that makes a fertilizer what it is.

They are a "strong compost" or strong compost ingredient.

In terms of their safety, I would not put a fresh pound onto one of my container tomatoes. I too would compost them first.

But in terms of the OP's question, I visualized someone with a in-ground garden, dumping each morning's coffee grounds as mulch.

We might both agree, no problem.

    Bookmark   June 10, 2014 at 1:17PM
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johns.coastal.patio(USDA 10b, Sunset 24)

lol, just noticed that that "organic materials" list include "jellyfish."

Years ago I was at a wedding. I was munching away with my chopsticks when my girlfriend said "you like jellyfish?" I look at her, I look at my plate, I look at her, and I say "yeah. yeah, I guess I do." Still funny to me.

    Bookmark   June 10, 2014 at 1:21PM
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i started using them " in bulk" about a year or more ago.
i get 50lb at a time from starbucks

you cant compost them unless you have a lot of brown material with it, or they just sit there.

if you lay themin the sun, they dry out, and turn brown. i think this decomposes them much faster.

I have used them straight in the ground without composting them, and while i dont recommend it for a "good" soil, it has worked for me in a couple of places where i had sand only with no organic matter.

composted is much better though.

also, they provide lots of micro-nutes like copper, zinc etc..
and supposedly, they release the N over time, which is a good thing.

    Bookmark   June 10, 2014 at 2:00PM
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I have used some at some point in my gardening straight into the garden, did not see any immediate difference. Plants did not look any better after than before. Off they go to compost but it is rare since we are not coffee drinkers 9 in general.

    Bookmark   June 11, 2014 at 8:38AM
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I remember my mother adding coffee grounds to the soil when we planted carrots. She said it was to ward off some bugs. Unless I'm remembering it incorrectly. I generally have a pretty vivid memory but in this case I was 6-7 years old so who knows.

    Bookmark   July 25, 2014 at 6:14PM
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To add to the NPK discussion, it really does not matter what nitrogen numbers that coffee is, if it not avail in the form plant can utilize then it useless and sometimes harmless to the plant. I do understand why people keep repeating put eggshells, put coffee grounds, put fish heads etc in your garden...

    Bookmark   July 25, 2014 at 10:56PM
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I've used coffee grounds twice before. Once on some suffering rose bushes that looked awful and within a week they flourished and looked better than ever and took on new growth and rose buds.

Then a couple months ago I put some grounds in a dying bamboo species house plant... the type that has 3 shoots in a pot. Due to lack of sunlight and indoor light 2 shoots died and the surviving one leaves yellow etc...
the results.. it's no longer dying and I no longer need to trim off dead leaves etc...

Personally I wouldn't put coffee grounds op top of tomato soil. I think I'll put some grounds over one of my sunflowers that isn't wanting to grow. It's remained tiny while all the others are huge now. I pored my urine on it yesterday and hope for it to help.

    Bookmark   July 25, 2014 at 11:26PM
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seysonn(8a WA/HZ 1)

I do understand why people keep repeating put eggshells, put coffee grounds, put fish heads etc in your garden...


People put eggshells in the soil as an immediate source of calcium to prevent BER. But coffee ground even not considering its fertilizing role , is a great soil amendment. And I think that it should not take it too long to be decomposed to release nitrogen in useable form. Things can be composted directly in garden soil too, not just in the compost pile.

Anyway, a 2% N is a significant amount , not found in most bagged manures. It should be available in useable form, eventually. Just forget the instant satisfaction expectation.

    Bookmark   July 26, 2014 at 4:59AM
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i had left an experiment in my garage out for a month
it had grounds i was using for mushrrom growing (failed)

anyway, it seemed to me, the grounds changed chemically
they had completely dried out.
i planted some seedling (papaya) in them with my normal potting soil (50/50)
and they are doing very good.
i think next time i will use %20 or %30 and more coarse sand, as papaya like very good draining soil though

so i took 40lb of grounds i had, and let them out to sun-dry.
will update later when i start growing with them.

    Bookmark   July 26, 2014 at 10:21AM
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Summary: Use of Starbucks coffee grounds in amending mineral soils up to 35 percent by volume coffee grounds will improve soil structure over the short-term and over the long-term. Use of the coffee grounds at the specified incorporation rates (rototilled into a 6- to 8-inch depth) will substantially improve availabilities of phosphorus, potassium, magnesium and copper and will probably negate the need for chemical sources of these plant essential elements.

The nitrogen, phosphorus, potassium "guaranteed analyses" would be as follows for the coffee grounds:

Nitrogen: 2.28 percent
Phosphorus: 0.06 percent
Potassium: 0.6 percent

Available nutrient levels: The pH or reaction of the coffee grounds is considered slightly acidic and in a favorable range at 6.2 on the pH scale.

Salinity (ECe) is a measurement of total soluble salts and is considered slightly elevated at 3.7 dS/m. The primary water-soluble salts in this product are potassium, magnesium, sodium and chloride. The potentially problematic ions in sodium and chloride are each sufficiently low as to be inconsequential in terms of creating problems for plants.

The availabilities of nitrogen, calcium, zinc, manganese and iron are quite low and in some cases deficient. Thus, the coffee grounds will not supply appreciable amounts of these essential plant elements when used as a mineral soil amendment.

However, the availabilities of phosphorus, potassium, magnesium and copper are each sufficiently high that there will be a very positive impact on improving availabilities of these elements where the coffee grounds are used as a mineral soil amendment. The coffee grounds will negate the need for additional sources of phosphorus, potassium, magnesium and copper when blended with mineral soils.

In summary, the available plant essential elements which will be substantially improved where the coffee grounds are used as a soil amendment, include phosphorus, potassium, magnesium and copper.

Total nutrient levels: Each cubic yard of these coffee grounds contains a total of 10.31 lbs. nitrogen, of which 0.01 lb. (0.09%) are available. Thus, even though available nitrogen is considered deficient in this product, there still remains over 10 lbs. of total nitrogen per cubic yard of coffee grounds. Thus, nitrogen is primarily bound in the organic fraction and is unavailable to plants until soil microorganisms degrade the organic fraction. Through this process, the nitrogen is converted to plant available forms. Over the long term the coffee grounds will act like a slow release fertilizer providing long-term nitrogen input which can then be utilized by plants.

Nearly all potassium and all magnesium are in the available forms. This means that immediate availability improvements for these two elements will take place when the coffee grounds are blended with mineral soils. About half of the copper and calcium are in their immediately available forms.

All other plant essential elements are primarily bound in the organic fraction and will thus be subject to slow release over time as soil microbes continue to degrade the organic fraction.

Physical properties: Virtually all particles passed the 1 millimeter (mm) screen resulting in a product which is very fine textured. Each cubic yard of the coffee grounds will supply an excellent amount of organic matter, measured at 442 lbs. organic matter per cubic yard. At the use rates indicated in this report, the input of organic matter will be substantial and will result in considerable short-term and long-term improvement of mineral soil structure.

Carbon/nitrogen ratio: On the basis of dry matter bulk density (452 lbs. per cubic yard), organic matter content (97.7%) and total nitrogen (2.28%), the estimated carbon/nitrogen ratio is about 24:1. This means that there is more than sufficient nitrogen present in the coffee grounds to provide for the nitrogen demand of the soil microorganisms as they degrade the organic fraction.

Use rate: Based on the overall chemistry and physical properties of the coffee grounds, they can be utilized at rates similar to other organic amendments when used in amending mineral soils. These data indicate that 25-35 percent by volume coffee grounds can be blended with mineral soils of any type to improve structure of those soils.

Here is a link that might be useful:

    Bookmark   July 26, 2014 at 10:22AM
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I had always heard that Starbucks is absolutely terrible for the environment. Okay... it's been very many years since they established their business and my memory is faded on the facts, but what they do and add etc is harming land.

I am a MAJOR coffee drinker and a place I worked at provided starbucks for free to drink as we wanted it while working. After drinking this s!@# for a couple weeks my body has rejected it.... it makes me sick in the stomach and for the past 12 years + anytime it is offered to me my body gives an alarming NO to not drink it again. In meanwhile I can drink any other brand by the loads.

    Bookmark   July 26, 2014 at 12:49PM
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Adding coffee ground to my sunflower its grown about a foot since so it def works. It hadn't grown taller for over a month.

    Bookmark   August 2, 2014 at 12:57PM
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