If you’re buying sustainably farmed coffee, like spinneysFOOD Organic Peruvian Andes El Palto Coffee, then you can do a little more for the environment by returning your used grounds to the soil as compost, mulch, or fertiliser. Certain popular myths about coffee have been as mixed up as beans in a blender - for instance, we can’t vouch for the common celebrity claim that a heated goop of coffee grounds and egg white can be applied to the skin as a cellulite treatment - but gardeners swear by the stuff for solid, scientific reasons, and we're here to help separate out a few useful facts from the fiction.
COFFEE MAKES GOOD COMPOST
Instead of filling the bin or blocking the sink, your grounds can be recycled through the compost heap. Their nitrogen-richness gives the existing bacteria an energy boost, and attracts more microorganisms to help break down the organic matter. Worms apparently like coffee too, and will join in that work with gusto when tempted by those extra nutrients.
COFFEE HELPS PLANTS GROW
This is only true up to a point – a common misconception is that the high acid levels in coffee beans make the used grounds a kind of elixir for acid-loving plants like tomatoes, roses and blueberries. Actually, most of that acid is neutralised on contact with water when you make your morning cup, and the waste material doesn’t add much to the soil. It does, however, help improve the retention and infiltration of air and water - which makes it a pretty good supplementary fertiliser and a useful mulching agent. For the best results, used grounds should be mixed with ‘brown compost’ elements like dry leaves or sawdust.
COFFEE REPELS ANTS AND MOSQUITOES
Studies show that the coffee grounds can keep away annoying insects, and even kill off larvae. You can add them to standing pools of water around your house, mix them with water to deploy as an insecticide with a pump spray bottle, or burn them in a tin can to create a scent that is quite pleasant for humans but apparently repellent to mosquitoes.
COFFEE KILLS SLUGS
Or at least caffeine does, in high concentrations. Used ground coffee probably doesn’t yield enough of the stuff to have that effect, unless really laid on in bulk, but when mixed with water and sprayed on plants it can deter slugs and snails from eating them.
COFFEE DETERS CATS
Evidence for this is essentially anecdotal, but you’ll know from your own experience that cats will almost always refuse a cuppa when offered. And many gardeners will tell you that used grounds spread across plant soil and flowerbeds can make any cat think twice about making a litterbox of your precious turf.
Spilling coffee on your clothes or bedside table is a pain. But you can use it to your advantage too, if you want to give a piece of wooden furniture a new look. Just soak the used grounds for a few hours and apply the watery mix in layers with a paintbrush to achieve your desired effect. The stain will darken nicely with every coat.