Anyone who knows me knows exactly what to buy when my birthday comes around – and it’s usually in the shape of new greenery and a tin of ground coffee. And I just can’t get enough of them. So, you can imagine my delight when I discovered a coffee ground trick that combines my passions.  The method in question involves putting my ground coffee waste to good use as a natural fertilizer for my best indoor plants. The process is quick (I create and add the grounds in a matter of minutes post-Saturday morning coffee), and it reduces unwanted waste. I’ve also practiced this routine across the calendar – meaning you can use it on your best winter houseplants –  and next spring and summer –  when the time comes. And it’s not just me who appreciates this neat trick. Judging from the health of my houseplants, I would say they do, too. Here’s what the process involves. 

How I use coffee grounds as a houseplant fertilizer

Despite my love for all houseplants, I’ll admit that low-maintenance indoor plants are my favorite. Why? Because they’re just so easy to care for. Since I opt for easy maintenance where possible you can imagine how happy I was to see this coffee ground trick is ultra simple.  To begin, I pour my coffee ground waste into a glass jug before adding a tablespoon of cinnamon and a medium-sized cup of soda water. I tend only to use grounds that have had two days to dry to ensure the solution is at its most effective. I then mix the ingredients together. My measurements are not overly strict, but it creates a mixture that is large enough to nourish a handful of plants.  After creating the mixture, I take my plants to my sink and pour directly from the jug until the soil is moist. It really is that quick. Then, I reward my efforts with a cup from my best coffee machine, naturally. 

What makes this coffee ground trick successful?

I measure this trick’s success by the health of my plants – I could tell something was working as it should. However, I couldn’t help but wonder, what makes coffee grounds so appealing to plants? The answer, according to plant expert Kevi Tara from LEAFnJOY (opens in new tab), is in the minerals.  ‘Coffee grounds are an excellent houseplant fertilizer due to their high nitrogen content (about 2 per cent) that releases slowly into the potting media as they decompose. However, coffee grounds have more to offer to plants than just nitrogen,’ she says. ‘They contain the full nitrogen-potassium-phosphorus range and then some more, namely important micronutrients such as calcium, magnesium, boron, copper, iron, and zinc.’ Kevi adds that our favorite living room, kitchen, and bedroom plants need both ‘micro and macro elements to thrive’ – meaning grounds are a great soil additive for healthy, happy plants.  ‘Apart from their nutritional composition, coffee grounds are slightly acidic with a pH between 6.5 and 6.8, which can improve the overall pH range of the potting media,’ the expert explains. ‘Most indoor plants prefer to be kept in slightly acidic soil at around pH 6 for optimal nutrient absorption, growth, and vigor.’  It is, however, important to note that you should only use pure black coffee grounds on your houseplants. If you’ve tainted your grounds with milk sweeteners or syrup, you may do more harm than good. At best, milk and sugar can attract fungus gnats (although we can share the secrets of getting rid of fungus gnats with you if you should need this advice) but, at worst, you could damage your plant. If you’re a coffee and plant lover, I have no doubt this trick will speak to you in the same way it did for me. And your plants may just thank you for that extra cup on a Sunday morning.