Coffee isn’t just a boost for us, it’s a boost for our plants too! Making coffee, even in a coffee shop with those beasts of machines, doesn’t extract all of the goodness from the grounds. Instant coffee too has its benefits. Using spent coffee grounds also has a big ethical benefit – 1 cup worth of coffee uses 150 litres per cup to grow, process, pack and ship! Then there’s another 6 litres of water that goes into a teaspoonful of sugar, then the milk….
I originally wrote an article for Pip magazine #21 on the topic of using spent coffee grounds for your garden but wasn’t too happy with the way they changed it around. Here’s the full scoop!
Once the caffeine and rich oils are extracted from the from the ground coffee beans there are still plenty of nutrients left in the spent grounds that can be used on our garden or even ourselves.
The main things that we are interested in are nitrogen, potassium and calcium and some trace minerals. Nitrogen is essential for producing proteins (particularly DNA and RNA) and enzymes. Potassium is essential for the balance of water in cells and calcium is used in making strong cell walls. Coffee, then can be an important booster.
Coffee grounds are mildly acidic but unless you dump whole pots of the stuff in one place, you’ll have no worries. Your thriving soil biology will take care of it for you. If you have any doubts, put the coffee into your compost or worm farm – the critters in those will balance things out for you.
If you’re using your own coffee grounds, made at home, you may need to collect some to make a big batch of coffee ‘tea’ for your garden. That doesn’t preclude emptying your pot out daily around the base of mature plants. Essentially, enough for 1 cup for you is enough for one mature plant. Just don’t apply too often.
If you have ask nicely at a local coffee shop or restaurant, the staff will probably be more than happy to give your their spent grounds as long as you bring a bucket. Just a note, one of those tubes that cafes dump their grounds into will fill a 10 litre bucket, so be prepared!
We get our grounds from a couple of cafes in Gawler who are part of the Gawler Compost Collective. Once a week, I pick up a 10 litre containerful from Cafe Sia and that is more than enough for our garden, the rest go to Uncle Rob’s Worm Farm. Maybe you can set up a similar thing in your area.
‘Coffee tea’ sounds funny, we are so used to thinking of coffee and tea as separate things but your garden doesn’t care. To make a bucket of coffee tea, simply soak a handful of grounds in a bucket of water. This will leach out the water soluble goodies. You can filter the coffee grounds out and then apply the remaining solution to your soil around the roots of your plants. There are so many variables in how strong your coffee solution will be, so I recommend using no more that 1 good handful of spent grounds to a 20 litre bucket of water. You can use that straight on the soil.
As a foliar spray, dilute the coffee solution with water at a rate of 20:1.
You can simply cast the spent coffee grounds onto the soil where their nutrients will be rapidly gobbled up by soil fauna and flora. The physical grounds are finely ground organic material and this will add to the organic content of your garden. Don’t put it on too thickly though, too much can clump together or form a compact layer over the soil which will prevent air, water and light from penetrating.
I suggest about 1 big handful per square metre.
Spread a small handful lightly over the surface of your worm farm. The worms will find it and love it.
If you are putting it into your compost, spread it evenly over the surface so that it can be mixed in the next time you turn your heap or bin.
You can add spent coffee grounds to your Bokashi bin, just as you would any organic material. You can also make your own Bokashi bran from spent coffee grounds and use that instead of the store bought stuff.
Instant coffee isn’t as potent as the coffee you brew from ground beans, too much has happened to it in the freezing, drying, packaging, shipping and storage process. However, it does contain traces of the goodies mentioned above and can be added (well diluted) directly to your garde. It doesn’t contain the organic component of the coffee grounds that give them the extra benefit of adding to your soil structure.