I have been asked a few times now about coffee grounds pH and their impact on the soil. During my research, I came across a good fact sheet from MSU, and you can find the link to learn more about pH levels and coffee grounds here.
As I’ve mentioned in my post The Ground to Ground Primer – Coffee Grounds for the Garden:
Used coffee grounds are slightly acidic, with a range typically between 6.9pH and 6.2pH. It would be higher except that most of the acid within the beans is extracted during brewing.
For many vegetable and ornamental plants, the desirable pH range is 6.9 to 5.8. A pH level of 7.0 is considered neutral, and from there it is increasing in alkalinity.
So you will find that there are very few situations where the slightly acidic nature of coffee grounds are going to be a problem, especially as most of it should be going into the compost and the rest straight into the garden.
I have heard of concerns with coffee grounds going into small pots, the type for indoor plants. If you are going to add them into pots, make sure you dig the grinds into the soil and avoid it just sitting on the top. Coffee grounds will form a top crust if left that way, blocking water and air movement.
If there are any problems with the link, you can find the PDF below.
Coffee Grounds for Plants According to pH
- Mould and coffee grounds (groundtoground.org)
- How does the chemical properties of the soil relate to soil fertility (wiki.answers.com)
Wow good on you for going into so much detail! Would have been in trouble without all the hard work you put into this post. Just one question, how different are different types of coffee grounds? Say if I have a flavoured blend or one that is not roasted as much? Is it even something I need to worry about… Waiting for you expect advice.
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Thank you for providing this information. I was never sure about what I could use all these coffee grounds for because of the pH levels, but will start adding to all the vegetable and fruit plants at my place. Cheers – DJ.
No worries David. Just keep in mind that coffee grounds for pots can cause some issues so use in reduced quantities and take it a little at a time. If the potted plant is doing well with the grounds then keep it at that level.
thoughtful post to go into plants and the p.h.