Coffee Grounds

Sliema, Malta

I've read that you can sprinkle used coffee grounds on the surface of the soil. Is this for both ground and container plants? Also, would these be beneficial to all plants? With regards to vegetables, I have rucola, speedy salad mixes, mint, parsley and am trying to grow cherry tomatoes and lettuce. Can I also sprinkle them on plants like geranium and succulents? thanks.

Prairieville, LA(Zone 9a)

Coffee grounds tend toward the acidic side, so use with care. A small amount mixed into the soil of acid loving plants seems to be okay. We mix egg shells and coffee grounds with water and let it set a couple days and use the water for container plants. The calcium in the egg shells balances with the grounds.We also add coffee grounds to the compost bin and when mixed well, the end result is a fairly balanced pH product. Below is an article from Gardens Alive (I included the link in case you want to look at it)

"Now, on to coffee grounds! When we first started doing this show, we warned people to only spread coffee grounds around acid-loving plants, like azaleas, rhododendrons and blueberries, because the grounds were bound to be acidic; and not to overdo it on those and other flowering plants, as the grounds were certainly high in Nitrogen, which makes plants grow big, but can inhibit the numbers of flowers and fruits.

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.)

But I had to quickly sputter that I never recommend adding anything to raw ingredients before composting for fear of upsetting the apple—eh, compost—cart. “Neither do I,” said Will; “this is a unique situation.”

And he certainly doesn’t think grounds should be used in their raw form. First, he explains, they are so acidic and so Nitrogen rich that you risk creating a ‘mold bloom’ where you spread them. And second? “There’s no life in those grounds; its all been boiled or perked away.” Instead, he suggests doing what the guy with that original sample did—adding the grounds to microbe-rich yard waste and composting that perfect combination. Will liked my suggestion of four parts shredded leaves to one part grounds by weight, but adds that even having grounds make up 10% of a pile of otherwise shredded leaves would create great compost.

Nutrient content? Will explains that the kind of coffee grounds a typical homeowner would produce or obtain are around 1.5% Nitrogen. There’s also a lot of Magnesium and Potassium, both of which plants really like; but not a lot of phosphorus (the “fruiting and flowering nutrient”) or calcium, a mineral that many plants crave, and whose lack helps explain that recalcitrant acidity. (“Lime” is essentially calcium carbonate, and wood ashes are also very high in calcium; click HERE for a previous Question of the Week that goes into great wood ash detail.)

So mix those coffee grounds in with some lime or wood ash and then into lots of shredded leaves; you’ll make a fine, high-quality compost. The only exception I can think of is our listeners out West cursed with highly alkaline soil; you could try tilling in some grounds alone and see if it moves your nasty soil towards neutral with no ill effects.

Otherwise, we can’t recommend their raw use; the acidity could be high enough to damage even acid-loving plants. And yes, this means that our poor New Jersey listener could be harming his plants with all that uncomposted coffee. Unfortunately for him, Northeast soils are ALREADY acidic; that’s why many homeowners in the North lime their lawns. And when I scrolled through those ‘testimonials’ that so swayed him, I noticed that they all seemed to be from California, where the soils are highly alkaline. And you can’t improve clay soil by making it more acidic or alkaline; the only way to REALLY improve clay soil is to dig it up and toss it into the woods!."

For lots more info about high quality testing of soils, composts and raw ingredients, visit the Wood’s End web site:

(Zone 7a)

I do what is suggested in the article and compost mine, filter and all.

Ayrshire Scotland, United Kingdom

I only add coffee Grounds, tea bags ect to the compost heal where it gets mixed with other waste, but friend add the coffee grounds directly to the garden especially if sat out doors with mugs of the stuff, anyway, nothing appears to happen to there plants as far as damage ect but then as the Moon has also mentioned, I think it would depend on the PH of the soil plus the type of plants they grow, my friends have a wide range of stuff so maybe because we live in a high rainfall area helps too.
I guess the best thing to do is give it a try in a pot over a couple of months, if the plants look like ther are in trouble then stop adding the grounds, If they are fine, then maybe widen the use.
Good luck. WeeNel.

Kure Beach, NC(Zone 9a)

I've used them in mature container plants occasionally with no ill effects. Once the grounds have been used, they aren't that acidic.
Here's an interesting article on the topic. Coffee grounds are talked about on page 8.

Magnolia, TX(Zone 8b)

Coffee grounds are candy to worms, add sparingly

Sliema, Malta

Thanks for all the advice, very much appreciated! :)

Prairieville, LA(Zone 9a)

You are most welcome.

(Arlene) Southold, NY(Zone 7a)

I'm with Kwanjin. I've tested them since people do love to believe they're acidic but they aren't. I scratch them into the soil, use them as a soil conditioner, and use them in our six compost bins. Worms love coffee grounds! They are excellent at holding moisture so for dry soil it's an easy answer, or for spots like under eaves, that don't get the rainfall.

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Springfield, GA

OK, I have read all your post and I am still a bit confused I have been living in south east Georgia near Savannah were the soil is a mix of sand and clay. I have read and heard so many stories about used coffee grounds and used tea leas I don't know what to use them for. I have heard to use the for all different types of lil bugs repellants to fertilizers....Someone PLEASE help me...I have I don't know what kind of banana trees that have been severally neglected by previous renter's, before me, but I care for where I live and the plants on the grounds I live. The Banana trees are regrowing after our harsh inter lil babies ( suckers) I think you call them, are popping out and i want to make them healthy the right way. I even have a Mediterranean Fig tree I have no idea how to care for but I am trying. Any and all advise is more than welcome..and most appreciative.Thank you to all

Ayrshire Scotland, United Kingdom

I compost all food waste as long as it is not meat, chicken, or anything that could or would encourage vermin to be troublesome around the compost heap as these type of creatures soon take up residence where there is a food supply.
So regarding Coffee Grounds and tea bags /leaves, like everything else, it's all in proportion, IF you were to add large bags of grounds to soil or even the compost heap, you could cause the soil or heap to become acidic IF they add to the acidic count, but then you don't go adding a huge amount of grass cuttings at the one time or lot's of pruning's from the shrubs, you mix the amount of stuff you add as you gather it, so I honestly cant imaging a normal household having enough coffee grounds to cause a huge problem assuming they are added along with other compostable waste. I look at is as everything in moderation just like my own diet ha, ha, ha.

Kure Beach, NC(Zone 9a)

Use them just like you would anything else that goes into your compost bin. If the coffee grounds are used, they won't make the soil acidic. Even if you added them fresh, directly into the soil, you would have to add a LOT all the time and once you stopped, the pH would go right back up.
Have you had your soil tested? Until you do, you really don't know what your pH is. You can get a good analysis done through your county's Cooperative Extension.

Ayrshire Scotland, United Kingdom

You can buy a cheap soil testing kit from the garden store for a couple of dollars and within about 2 minutes you will have the results, the instructions are really idiot proof to follow believe me I need simplicity, don't buy any expensive testing kits as the cheap ones do the exact same job.

It would be worth your while to test a few areas in your yard as there can be discrepancies from one area to the other, My ground for instance is classed as acidic and sandy soil, over the years I have been adding loads of humus and manures so the soil in those areas has altered and in other areas where there has been a lot of leaf mould, the readings are different, so to be able to grow different types of plants / shrubs and trees, it is helpful to know where humus is required, or peat to keep the acidity up should be put, then you don't throw good money away by growing the wrong plants that need different soil types.

Hope this helps you out a bit and if your still unsure, then as Beach_Barbie has said, go to your local County extension office.

Kure Beach, NC(Zone 9a)

Exactly Weenel, until you know waht your soil is like, you won't know what it needs or what plants will do well where.

(Arlene) Southold, NY(Zone 7a)

Coffee grounds and tea leaves act as soil conditioners and help the soil retain moisture. I wouldn't go around sprinkling them on plants but I do incorporate them into the soil. Sorry, I'm no help with banana plants.

Kure Beach, NC(Zone 9a)

I didn't say anything about banana plants and I do have experience with them (sorry!).
They are not that picky about pH. I give mine lots of water and fertilizer (I use 10-10-10) and have kept them happy enough (with Winter protection) that I have gotten bananas!
I suppose there is a "banana fertilizer" out there, but for me, just using a balanced fertilizer worked great.
BTW - the banana babies are called "pups." ;)

(Arlene) Southold, NY(Zone 7a)

It was tangey524 who mentioned banana trees. Long Island will never be noted for bananas! Ducks and potatoes but no bananas.

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