What to do with leftover coffee???

eaglesgarden(6b - se PA)August 19, 2010

I know that UCG work well in a compost mix, whether VC or standard pile. The question is what should I do with the leftover coffee itself. Almost every day, my wife and I generate 2-4 (sometimes 6) cups of extra coffee. We drink a ton of the stuff, but sometimes she will make some for herself (and make extra for me, expecting I want it, but I've already exceeded my quota) or vice versa. Anyway, it seems like such a waste to just throw it down the sink. I know that coffee would benefit SOMETHING in my garden, the question is what?

I think my two little blueberry bushes might be the best option. Can I just pour the excess (after it has cooled) at the base of the blueberries? Would it end up TOO acidic, even for the blueberries? Should I just pour it on the compost heap? What other applications are there for used coffee (not UCG)?

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digitaldan1(z7 NJ)

I've been diluting mine (about 10 parts water to 1 part coffee) and using it to water my plants.

I read a long time ago that you could use coffee to feed tomato plants and have done this from time to time. I also read a very long thread somewhere on these forums (I'm pretty sure it was the tomato forum) where the consensus was it wasn't a great idea. Seeing as those people know a heck of a lot more than I do about this stuff, I've changed that particular habit.

I've read elsewhere (I'm OCD and have broadband internet access) that pouring coffee into the compost pile is fine.

    Bookmark   August 19, 2010 at 8:28AM
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There's a FAQ here on coffee *grounds*,

but it does not mention the acidity or pH of brewed coffee itself. I thought someone had experimented with that here, but anyway, it's much more acidic than the used grounds.

I think it would be great for blueberries but the quantity you're generating might be too much for two plants. Digitaldan's practice of diluting is a good idea IMO.

Or you could pour it in the compost bin, in hot weather it's probably in need of water.

What I do is use it for iced coffee in the summer! Turn it off before it cooks too long. When cool pour into an ice tray. Keep some in the fridge too. After lunch when you're hot and sleepy, pour a glass of cold coffee, add cream and the sweetener of your choice, or maybe a shot of Bailey's ;-), and add coffee ice cubes. Voila, it'd cost you 3 bucks at that coffee place, the coffee ice cubes means it won't dilute as they melt, and the chill will take away at least a moderate amount of overcooked old coffee taste. Try it, you'll like it!

    Bookmark   August 19, 2010 at 10:24AM
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nygardener(z6 New York)

I'd pour it over the compost. Compost can always use moisture, and whatever solids are dissolved in the coffee will do your plants more good once they're composted anyway.

    Bookmark   August 19, 2010 at 11:33AM
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dottyinduncan(z8b coastal BC)

Good question eaglesgarden! I wondered about this too. I usually only have about 1 c of left over coffee and I've been diluting it and pouring it on my rhodies (they are handy to the kitchen), particularly one that was transplanted and didn't look happy. I believe it is doing better than it has ever done in previous summers. It is about 30 years old. Unfortunately, as an experiment it doesn't count because it has been transplanted into a shadier place so maybe it is happier because of the shade rather than the coffee. I live in the pnw so we already have acidic soil from all of the firs in the area.

    Bookmark   August 19, 2010 at 12:44PM
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chinamigarden(z5 MI)

Not sure what you mean by left over coffee. Never had that happen before

    Bookmark   August 19, 2010 at 1:35PM
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eaglesgarden(6b - se PA)

Thanks for the responses.

toxcrusadr - iced coffee is gross to me. My wife enjoys it a little, but fresh, not old. I am addicted to coffee, I won't deny it, but I have to have it hot and fresh! I can't stand old or iced coffee. So, while your suggestion would work for some, it will not work for me. Thank you though, I'm sure someone will find that suggestion helpful.

chinamigarden- it didn't used to happen to me before either! But, as I get older, health concerns have caused me to limit my coffee (read caffeine) intake. I am already on cholesterol medication, and a natural connection to high cholesterol is high blood pressure. I don't have HBP yet, but caffeine does increase BP, so I am working on keeping it under control. The bigger issue is that my wife and I wake up at very different times (I wake up early as an good gardener would, whereas she prefers to sleep in more). And we both like fresh coffee. So, when I get up and have mine, she throws the remainder out and makes her own! And when I want another cup...repeat! It's not the best solution monetarily, but it sure is tastier! Maybe we should just get a Kourig with individual cups of coffee! :^)

digitaldan - I think the dilution is a great idea. 10:1, that's easy to do! I guess it would work on almost any plant that prefers acidic conditions. My azaleas would probably enjoy it too!

Concerning the compost heap - I thought there were concerns with pH with coffee grounds (which appear to be unfounded, for the most part) but I know that coffee is acidic. Would I need to balance it with some baking soda or anything like that?

    Bookmark   August 19, 2010 at 6:25PM
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tapla (mid-MI z5b-6a)

Forum discussions frequently center on the question of adding dilute coffee/tea or grounds to plants as a 'tonic', but Arabica (coffee) and Camellia (tea) are known for their toxic alkaloid (caffeine) content and their allelopathic affect on plants as well as autotoxic (poison to their own seedlings) effects on future generations. Caffeine interferes with root development by impairing protein metabolism. This affects activity of an important bio-compound (PPO) and lignification (the process of becoming woody), crucial steps for root formation.

We also know that the tannins in both coffee and tea are known allelopaths (growth inhibitors). There are ongoing experiments to develop herbicides using extracts from both coffee and tea that cause me to want to say they might serve better as a nonselective herbicide than as a tonic. I would not use either (stale coffee or tea) by applying directly to my plants - especially containerized plants; nor would I add tea bags/coffee grounds to my container soils.

Whoever mentioned spilling it onto the compost pile gets my vote as having the best idea so far.


    Bookmark   August 19, 2010 at 7:01PM
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Get yourself a new coffee pot. I like fresh coffee, too. There's 4 cup pots that will make what they call 2 cups, which is barely enough to fill a regular coffee cup. =:)

I could be wrong, but if you get one of those expensive pots with the individual coffee pods, I'm pretty sure the plastic pods are not recyclable. With the amount of coffee you're drinking, that's a lot of garbage, plus they're expensive.

    Bookmark   August 19, 2010 at 7:25PM
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eaglesgarden(6b - se PA)

Thanks Al!

I want to do what's best, and certainly don't want to do something detrimental to my plants!

    Bookmark   August 19, 2010 at 7:34PM
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sandhill_farms(10 NV)

Just take your left over coffee and pour it somewhere on your garden or in your compost bin. Frequently pour it in differnt spots and you'll be fine, it's not going to hurt anything unless you overdose one spot. In our old house we had an aluminum can crusher mounted outside the backdoor. Underneath the can crusher was a potted rose bush. Before we'd crush the cans we'd dump whatever was left over in the cans in to the potted rose bush and that bush was the fullest and greenest rose bush we had. I doubt that you'd have any problems with your leftover coffee just pouring it somewhere in your gardens.

Southern Nevada

    Bookmark   August 19, 2010 at 10:54PM
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I'd pour it on the compost or use it to water acid loving plants like azaleas, rhododendrons, etc. If you have problems with slugs or snails, I'd boil it to concentrate it and spray it in the areas where the slugs and snails are a problem (as is it wouldn't do much, but concentrated it may kill them).

    Bookmark   August 20, 2010 at 12:35AM
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tapla, very interesting info on the allelopathic properties. I had not heard about that. The big question in my mind is the dose - do they actually harm plants at a concentration or dose that could realistically occur in the average household? Not trying to be a skeptic here, but "the dose makes the poison" as the Greeks used to say. :-)

    Bookmark   August 20, 2010 at 12:09PM
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tapla (mid-MI z5b-6a)

It probably does (dose/poison), which is why I drew some delineation between containers and the garden. While I don't think it would create noticeable problems in the garden, and especially not if you spilled it onto your compost pile, it's likely to impact container plants more - even if we don't see it. There are lots of practices many of us adhere to that got their starts in faulty observations turned anecdote turned something like urban legend (like misting houseplants).

I often look at some of the things people do to/"for" plants in terms of lost potential. The loss may SEEM intangible because our observational skills are either not acute enough to detect it, or the loss of potential goes completely unnoticed. You may not be able to quantify lost potential w/o a controlled experiment, but that doesn't mean it's not still there.

Not to change the subject, but a very good example would be the practice of using bloom-booster (high in P) fertilizers for their containerized plants, thinking they really DO improve blooming. Plants use about 6X more N than P, and there is no part of the growth cycle where they even come close to using as much P as N - so why would we ever use fertilizers that supply so much P? They don't improve blooming or fruiting, and they do affect growth in a negative way, even if you cannot see it. The 'overdose' of P interferes with the uptake of several nutrients. N is among them, but it also particularly affects uptake of Fe & Mn, not to mention it unnecessarily adds to the EC/TDS level of the soil solution and raises pH. High-P fertilizers may not kill your plant or cause it to grow in a way that you can't live with, but it does affect their ability to grow to their genetic potential within other cultural limiting factors - I look at the leftover coffee thing with the same guarded eye.


    Bookmark   August 20, 2010 at 1:34PM
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Cold coffee is a good slug repellant when sprayed on plant leaves and many people have for yers used cold tea to water plants with no apparent adverse affect so I'd think coffee could do the same.

    Bookmark   August 21, 2010 at 6:30AM
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lizziem62(z4 Ont.)

i pour any leftover liquids into my compost. coffee/tea/pop/ pickle juice/rinsings from jam jars, ketchup bottles.

i always thought it was doing well, adding that much needed moisture in the summer

    Bookmark   August 21, 2010 at 6:59AM
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Down the drain, Too far to compost pile, too wet for the worms.

    Bookmark   August 21, 2010 at 2:17PM
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This is an article on using coffee grounds for scale:


    Bookmark   August 23, 2010 at 3:25PM
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I use leftover coffee on my tomato plants. They seem to love it. Sometime they develop a touch of leaf roll from the extra nitrogen but then they end up fuller and greener than ever.

    Bookmark   May 17, 2011 at 11:42PM
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albert_135(Sunset 2 or 3)

* Posted by kimmsr 4a/5b-MI (My Page) on
Sat, Aug 21, 10 at 6:30

Cold coffee is a good slug repellant when sprayed on plant leaves and many people have for yers used cold tea to water plants with no apparent adverse affect so I'd think coffee could do the same.

Abstract of an article published by Harvard (Abstracting service I think.)Pest Control: Caffeine as a repellent for slugs and snails

    Bookmark   May 18, 2011 at 4:12PM
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kqcrna(z6 SW Oh)

Never any leftover coffee in my house.


    Bookmark   May 18, 2011 at 5:13PM
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Blueberries: not just the coffee, but the coffee & tea grounds too.
Coffee grounds are good for earthworms too.
But once the coffee grounds are composted, like oak leaves or pine needles, they raise on the pH scale.

Here is a link that might be useful: Ground coffee.

    Bookmark   May 18, 2011 at 6:20PM
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mustard_seeds(4 -Onalaska Wisconsin)

If it is just later in the day I drink it iced. But if it is the next am it is just easiest for me to dump stale coffee in the kitchen waste bucket that goes out later to the compost container once a day. If I were to carry a glass carafe outside I would likely drop it to pieces.

    Bookmark   May 18, 2011 at 6:43PM
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Maybe I can use coffee grounds for a hydrangea in alkaline soil that I want to bloom blue? Or the leftover coffee, if any.

    Bookmark   May 19, 2011 at 12:10PM
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tommysmommy, that should work.
My mother had one that was to big to reach around.
She told us to put tea & coffee grounds on the left side of it. The nurseryman I worked for, gave me a pinch of lime to put on the right side & we had a two tone Hydrangea.

Note: many of the new hybrids will not change color.

    Bookmark   May 20, 2011 at 12:24PM
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