Maybe you're one of many people trying to reduce the amount of trash you produce. Maybe you're wondering why your local coffee shop is giving away its waste coffee grounds to gardeners. Or maybe you're just looking for a free source of fertility for your garden. The answer to all three is that coffee grounds are easy to use in the garden, to make compost or as plant food.
To compost with coffee:
- Source your coffee grounds. If you can't function without a proper cup of coffee in the mornings, then you may well brew your own. If so then you have a ready supply of coffee grounds to use in the garden. If you're not a coffee drinker, or you don't have a coffee machine, then you'll have to hunt down a local coffee shop that gives its waste grounds away - or maybe there's a coffee machine at work you can empty.
- Use them fresh. Because they're damp and full of nutrients, coffee grounds quickly start to go moldy. Moldy coffee grounds are still fine to use, but they don't look as nice so you may want to compost them instead of using them as a mulch.
- Mulch. If you're after a low-maintenance garden, then you can simply toss your waste coffee grounds onto the soil as a mulch. Their dark color absorbs heat from the sun and can help the soil to warm up, and they'll add nutrients to the soil as they break down.
- Deter pests. Another advantage of using coffee ground directly on the soil is that it can deter pests. Slugs and snails aren't fond of the caffeine or the gritty texture, and might go elsewhere for a munch. If you have a problem with cats using your garden as a litter box, then a coffee mulch can help to disguise the smell and encourage them to 'go' elsewhere. And if you've got access to a regular supply of coffee grounds, then it's worth experimenting to see whether the smell confuses carrot flies, and other pests that find their way to your plants by smell.
- Make a liquid feed. Put about a pound of coffee grounds into a bucket or watering can with 5 gallons of water, leave it to warm up for a little while, and you've got a nitrogen-rich feed that you can use on hungry plants in your garden. The resulting feed will be slightly acidic - good for use on acid-loving plants (such as camellias, azaleas, gardenias, hydrangeas, rhododendrons, and blueberries). You can use it elsewhere, but keep an eye on your soil pH by testing your soil each season with a soil pH meter or garden chemistry test kit.
- Add coffee grounds to your compost heap. If you have a compost heap, then you can add coffee grounds - filters and all - to your heap. The carbon to nitrogen ration of coffee grounds is around 20:1, which means that it adds a nitrogen boost to your heap that can kick-start the composting process or compensate for a lot of carbon-rich 'brown' materials (woody plant stems, crumpled paper or cardboard). The C to N ratio of coffee grounds is similar to that of grass clippings, and because it has been ground up, it has a large surface area and breaks down quickly.
- Give your worms a boost. You can also add coffee grounds to your worm composter - the worms will love munching their way through them. In a worm composter, you'll need to keep a careful eye on the pH levels to keep your worms happy. Balance out the acidic coffee grounds with some lime, or crushed up eggshells.
If you're a real coffee addict, then you'll also appreciate the final bonus it brings to your garden. Everywhere you go in your garden, you'll get that fresh coffee aroma!