Coffee grounds poisonous?
Last post 06-08-2008 6:50 PM by Notsogreenfingers. 18 replies.
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25/07/2008 12:32 PM
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- JamesA
- Peterborough
- 24 Aug 2006
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160
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I've an esspresso every day and want to know what I can do with the coffee grounds.
People say you can use them to deter slugs, or put them in your compost.
I'm sure I read somewhere that coffee can be poisonous to plants.
If I put them around my veg plot and it rained they'd be in the soil.
I'm tempted just to put them in the compost, but I wondered if people on here have some knowledge of the science.
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25/07/2008 10:25 PM
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- Phot's-Moll
- The sunny South coast.
- 06 Jan 2007
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3,347
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They do help to deter slugs - a bit. It wouldn't be a good idea to put grounds on the same plant every day, but a small amount shouldn't hurt. I put my coffee grounds on the garden and it doesn't seem to do any harm. I don't drink coffee every day though.
Whether you think you can do a thing, or think you cannot, you are right.
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25/07/2008 11:00 PM
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- Anemone
- County Down, Northern Ireland
- 08 Feb 2008
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575
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I definitely remember reading on Alys Fowler's blog a while back that she got huge quantities of coffee grounds from her local cafe(s) to put round plants at Berryfields to protect from slugs. I can't see her doing that if there was any risk of poisoning the plants.
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26/07/2008 10:40 PM
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starbucks gives away coffee grounds to anyone who wants them. i should think it's less harmful than some chemicals on the market, though i don't know for sure.
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28/07/2008 09:54 AM
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- JamesA
- Peterborough
- 24 Aug 2006
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160
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Maybe they were just refering to too much coffee affecting the PH of the soil..
I'd better get drinking, I've got a coffee wall to build 
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28/07/2008 10:12 AM
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- Phot's-Moll
- The sunny South coast.
- 06 Jan 2007
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3,347
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Caffeine is a poison (so are many other things that we eat and drink) but not harmful to people in small quantities. Maybe pure caffeine watered onto plants kills them (Which seems likely) and that's why coffee grounds have got a bad name?
Whether you think you can do a thing, or think you cannot, you are right.
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28/07/2008 01:02 PM
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Coffee grounds are an Ok source of oganic matter for compost bin or even adding to the soil. The Bogweevil staggers down to the end of the garden each morning in his threadbare dressing gown to add the grounds to whatever plant needs a drink and washes the cafetiere out at the rainwater butt to water containers etc.
As for slug control, well they do have an effect but caffiene is said to be very harmful to a wide range of soil organisms especially worms, possibly worse then slug pellets which are at least reasonably specific to slugs.
Boggy
Beware the bat-eared bogweevil
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28/07/2008 02:36 PM
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- sue1002
- Ipswich, Suffolk
- 06 Sep 2005
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5,200
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"Stagger down the garden" - I thought coffee was supposed to help wake or sober you up
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28/07/2008 04:47 PM
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I am not good in the morning.
Boggy
Beware the bat-eared bogweevil
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28/07/2008 08:05 PM
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- Digger
- Northern UK
- 18 Jul 2005
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4,743
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I know that feeling well, I need a good few mugs of coffee in the mornings.
digger 
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04/08/2008 07:11 PM
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I don't really know if coffee grounds are poisonous to plants, but they definitely increase the acidity of the soil - they are VERY acidic. & they contain a lot of nitrogen. Even an ericaceous plant would not be able to tolerate the high acidity if given grounds every day. I give my husband's coffee grounds to my blueberry bushes but only do it once every week. & you have to gently work it into the soil, just dumping it on top isn't good (as it'll cake over time). Otherwise I pop the grounds into the compost heap to add in with the other goodies in there: worms love coffee grounds So, if you are going to use loads of grounds or if you're going to do it everyday, give it to your compost heap.
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05/08/2008 08:04 AM
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Coffree grounds are not acid and they are not rich in nitrogen and once you have stewed them in hot water they contain nothing very much. Were they acid or rich in nitrogen worms would avoid them.
Boggy
Beware the bat-eared bogweevil
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05/08/2008 02:31 PM
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- Susiq
- Northumberland
- 16 Feb 2008
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1,104
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er - does the same apply to tea leaves caffeine-wise? My mam keeps insisting I throw her tea leaves from the pot along with some water to swill said teapot out into the rosebushes (she is only one in household still drinking tea the 'proper' way - we use T-bags!) I compost our t-bags.
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05/08/2008 07:24 PM
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Boggy is right re: acidity. I'd assumed that since coffee was acidic, so too would be the grounds - can you tell I'm not a coffee drinker & believed what my Nana told me? But for the grounds when they decompose they do release nitrogen, it's perhaps not as much as I thought it was, but they do release some. Here's an actual research report done by Sunset (a respected gardening & West coast lifestyle magazine) in the States which my sister told me about when I asked her about the coffee ground question: http://www.sunset.com/sunset/garden/article/0,20633,1208232,00.html Hope that article offers some true scientific basis for your question now.
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06/08/2008 08:48 AM
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I cannot open your link, but be aware that all plant matter releases a smidgen of nitrogen when it decomposes which is why you add it to compost bins and why it turns into compost.
I would guess the article in question refers to Starbucks desperate search for good publicity and a cheap way of disposing of coffee grounds - these are no worse that other compost bin feedstocks and like all other materials should not dominate the process.
Boggy
Beware the bat-eared bogweevil
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