What can you do with coffee grounds in the garden? Is it possible to sprinkle them directly around fruit trees?
Each year, millions of tonnes of coffee grounds are produced worldwide, and because they are an organic material, recycling them in the garden makes sense. They are widely regarded as an excellent soil amendment, particularly for acid-loving plants like blueberries, rhododendrons, azaleas, gardenias, and daphne. Coffee grounds are said to repel slugs and snails due to their coarse texture.
However, are these assertions true?
Coffee grounds contain a high concentration of nitrogen and range in pH from slightly acidic to neutral to slightly alkaline. They degrade rapidly and any acidic effect, if present, diminishes rapidly, so they do not significantly alter the soil pH when used as mulch around plants. Additionally, they contain caffeine, tannins, polyphenols, and lignin, all of which have been shown to inhibit young plant growth and inhibit seed germination.
Regrettably, their rumoured ability to repel slugs and snails did not pan out at my house. Snails waltzed over coffee grounds barriers to munch on lettuce seedlings, and giant slugs appear to be attracted to the layers of coffee grounds in the worm bin.
On the other hand, you can use coffee grounds’ growth inhibitory properties to retard weed growth in garden beds that will not be used for six months or more.