I kept coming across patches of fine brown stuff around the base of plants in some of the gardens and the owners told me they are coffee grounds – they help to “improve” their plants. Now I had heard about the wonders of coffee grounds before but I had also come across a few notes of caution so I wanted to find out whether or not used coffee grounds were good or bad for your plants. And the answer is, they are bad. So why are used coffee grounds bad for your plants?
I am going to keep this short – for more detail I have added a few links to the end of the article that go into this in way more detail and offer links to the actual research material.
OK, let’s get started…
Used coffee grounds are often just dumped around the base of a plant and by their nature (uniform sized small granules) means they form a hard dense cap which means water runs off which means… less water for your plant.
Used coffee grounds have a substance in them… ermm… oh yes… caffine(!)… and that actually suppresses the growth of plants including the plant you are spreading them around!
If you were hoping used coffee grounds would help particular acidic loving plants then you are going to be very disappointed. They contain little acidity because whilst the unground coffee is acidic the used grounds are not because all that acid went into your coffee!
And that is that?
So it seems like the only useful thing you could do is chuck your used coffee grounds into the compost bin then where they can add to your brown ingredients. Oh dear, sorry to disappoint, but that is also not a good idea either – used coffee grounds also contain antiseptic properties. Which means they will make life more difficult for microbes, bugs and worms in your heap – the opposite of what you want!
In reality unless you are shovelling sacks of used coffee ground into your compost bins, they will be fine with your day to day grounds just be sure to give things a bit of a stir now and again.
Need more information…
Hopefully you have some food for thought now and to find out more, the following should be a good starting point.
- 5 Reasons You Should NEVER Use Coffee Grounds In Your Garden (Rural Sprout)
- Gardens: so you think coffee grounds are good for plants (Guardian)
- A Common-Sense Guide to Using Coffee Grounds in the Garden (Grow Veg)