Coffee grounds are rich in nitrogen, which means they’ll help a compost heap to decompose more quickly – and you can even throw the paper filters on the heap too. If you don’t have a compost heap, you can spread the grounds directly onto the soil as a mulch. Rainwater will wash the nutrients out of the coffee and into the soil, and a thick layer of grounds will help warm the soil and protect delicate plants or bulbs. In addition, slugs and snails aren’t as fond of caffeine as we are, and faced with a layer of coffee mulch might decide to quit your garden for easier pickings. Using coffee as a mulch can also help to deter neighbouring cats from using your garden as a litter tray, as they’re said to dislike the strong smell.
If you don’t have a compost heap or flower beds, treat your window box plants or tubs to an occasional feed made with coffee grounds. Dilute a few good handfuls of grounds around 1:40 with lukewarm water to produce a feed that’s rich in nitrogens. Plants with dark green leaves tend to love nitrogen, and will be particularly grateful for a little leftover coffee. These plants include rhododendrons, camellias and hydrangeas as well as vegetable plants such as Brussels sprouts and rhubarb.
If your garden is tiny or non-existent, or you don’t think you’ve got green fingers, why not put a sign up offering leftover grounds to local gardeners – it’s a shame to let all those lovely nutrients go to waste.