The problem
Coffee lovers often wonder if waste from their morning habit can feed their plants. The internet says yes; coffee grounds are packed with nitrogen and organic matter, in theory making them a natural fertiliser and pest deterrent. But can the dregs from your cafetiere really replace plant food, or will they do more harm than good?
The hack
Adding used grounds to your plant’s soil provides a nutrient boost and improves soil texture. Some also sprinkle them directly on to the surface of pots to deter pests. It sounds like a sustainable dream come true – recycling waste into nourishment – but it’s not quite that simple.
The method
Used grounds are slightly acidic and dense. Sprinkled thickly, they can form a crust that repels water and suffocates roots. Instead, mix small amounts into compost (no more than 10%), or add to an outdoor compost heap where worms can break them down properly. Never dump fresh, wet grounds straight on to houseplants.
The test
I mixed a few tablespoons of dried coffee grounds into the soil of a spider plant. I didn’t observe any crazy growth spurts or any signs of damage, but when I tried watering the pot directly, the soil compacted and water pooled on the surface. Clearly not ideal.
The verdict
Coffee grounds are great for compost but risky for pots. Used sparingly and well mixed they add nutrients, but on their own they can smother roots. Think of them as a soil additive, not a fertiliser.
