Coffee Grounds help your plants grow. Fact or fiction?
Many sources say they do, but one, in particular, said they looked worse!
I’d just dump my daily coffee grounds on the surface as a mulch once they had cooled (the way books and blogs suggest), creating a beautiful dark inch-thick layer of coffee compost by the end of the summer.
The crop yield and growth of pretty much everything in the coffee bed became noticeably worse within about two weeks of application. Plant growth slowed, some developed leaf yellowing, others defoliated and died. Seedling germination in some cases was almost completely inhibited. While some species looked OK, none of the plants in the coffee group proved better than my basic control.
– James Wong from his article in The Guardian
He also went on to say:
So I had a look at the scientific literature, and frankly I kicked myself. Coffee grounds are of course a rich source of caffeine – in fact they can be richer than coffee itself, depending on brewing technique.
There is a stack of studies to suggest it also stalls root growth in young plants, preventing their uptake of water and nutrients.
So why do garden centres and coffee shops give it away for your plants then?
There is much evidence to prove that whilst many plants do well such as this:
This however is down to the theory that the acidic coffee grounds give the Hydrangea plant a more blue colour, whilst more alkaline soils give the same plant a more pink to white yield of flowers.
With that said, this article (from the same website!) discusses how coffee grounds do not actually increase acidity of the soil.
So, which article do we trust?
Well, these articles could have been written by different people with different opinions.
Yes, some people claim that it releases nitrogen into the ground.
But some other people claim it inhibits root growth.
Some people claim it prevents pests from getting to the plants.
But some other people claim it reduces the drainage of the soil.
Some people claim it improves the drainage of the soil.
So why do so many people swear by it?
It must have some truth to it, otherwise no one would be doing it right?
Whilst it is popularly believed to be the case, just keep an open mind here and think that maybe it doesn’t have anything to do with the coffee grounds. Maybe they just had a good summer. Maybe the “tremendous growth” that their plants have been getting is due to a little more rainfall this past year. Who knows?
Overall, I would say that it’s definitely not essential to put on your garden bed or indoor plants. If you have some coffee grounds left over, it won’t do the plants much harm if you spread them over on the odd occassion. Is it really worth debating whether or not the benefits outweigh the downsides?
Oh, and if you want to know more about the pH scale of you soil and you don’t have a Hydrangea to judge by the colour, consider buying a pH tester. Click on the image below to go straight to Amazon to buy one!