You’ve enjoyed a cup or two of java from your cafetière or filter coffee machine and you’re going to throw the grounds out, but STOP RIGHT THERE. You can use coffee grounds in gardening for a whole host of plant-benefiting ways.
Even if you already put coffee grounds into the food waste bin to avoid them going into landfill, using coffee grounds in your own plot is more eco-friendly, as they won’t require heavy transport to take them away.
Using coffee grounds is a great method for pros and beginner gardeners also. From which plants love coffee grounds, to those that don’t, how to boost your compost heap and more, check out our hot coffee ground tips below – pun intended.
1. Make your own fertilizer for plants
You can create your own fertilizer from coffee grounds, saving the expense of buying a commercial version. Fertilizers are used to provide a source of nutrients for plants and improve their growth and, even if your soil is healthy, they could result in a better display from flowering plants and a bigger harvest in kitchen gardens.
Coffee grounds contain nitrogen, potassium and phosphorus along with micronutrients. If you’ve ever checked out fertilizer pack labels, you’ll know that these are the main ingredients – and there they are in the coffee grounds. That’s why some plants really benefit from the addition of coffee grounds. According to coffee expert Lewis Spencer of Coffee-Direct.co.uk ‘Coffee grounds have a varied amount of essential nutrients in each batch, but they all contain nitrogen, potassium and phosphorus alongside micronutrients. Plants such as carrots, azaleas and roses would appreciate a nice boost from coffee grounds.’
There are some plants however where coffee grounds could do more damage than good as they are highly acidic. Namely: Tomatoes! ‘However, tomatoes do not like the grounds.’ says Spencer.
All you need to do is sprinkle the grounds on the soil beneath plants and rake them in lightly. You can also make your own liquid plant fertilizer as well. Fill a bucket with 5 gallons of water and mix in two cups of brewed coffee grounds. Leave overnight before using.
2. Use coffee grounds in compost
Compost is also vital for healthy soil, improving its condition so air, water and nutrients are available for plant roots – and coffee grounds can be a great addition to your compost heap.
If you know how to make compost then you’ll know that it’s made using both brown ingredients – that’s things like dried leaves, twigs and newspaper – and green materials, including grass clippings and dead flowers. Coffee grounds can contribute to its green ingredients. Add the filter paper, too – only if it’s unbleached – which can be part of the mix and means you’ll be generating even less household waste.
3. Add coffee grounds to mulch
Using mulch in the garden has an array of advantages. It can help soil retain water, reduce weed growth (hurrah), and protect plant roots in winter. Coffee grounds can help out here, too, as part of mulch ingredients.
Mix the coffee grounds with other organic matter – think leaf mould. It’s a way to reduce the risk of clumps which could stop water reaching plant roots. Make sure you don’t use a thick layer either because plants could be sensitive to the caffeine in the grounds.
4. Natural pest control – stop slugs and snails
Stop these pesky plant devourers in their slimy tracks by cleverly using coffee grounds in gardening. Yep, coffee grounds can create a barrier between slugs and snails and the tender plant growth they like to chomp their way through.
Just spread the grounds around the plants to deter their advance; apparently they really don’t like caffeine.
5. Feed worms with coffee grounds
Worms, or at least the sort that you’d use in a wormery, are fans of coffee grounds, it seems. If you’re are a vermicomposter – or like the idea of becoming one – coffee grounds can be part of the kitchen waste you add to your worm bin.
Vermicomposting employs the skills of particular types of worm to turn scraps from the kitchen along with other green waste into both compost rich in nutrients and liquid fertilizer.
You can add a cup of coffee grounds a week to a small worm bin. Make sure you never put in too much Which plants like used coffee grounds?at one time, though, as the acidity could be a problem. Oh, and you can add the paper paper filter as well. Neat!
Which vegetable plants in particular like used coffee grounds and why?
‘As coffee grounds are close to pH neutral, acid-loving vegetable plants will benefit the most. This is because the grounds lead to better harvest by providing extra nutrients. Cabbage, carrots, potatoes, radishes, turnips, squash and soybeans all like used coffee grounds.’
Can you put too much coffee grounds in your garden?
If your soil already has a high level of nitrogen, adding in coffee grounds could take the level over the edge, actually stunting the growth of some plants.
Spencer adds, ‘Be careful not to add too much coffee grounds into your garden as the small particles can clump together creating a water resistant barrier, stunting plant growth. Always use the grounds sparingly and never in large quantities. Coffee grounds will not kill grown plants, it will just take some recovery time in the event of excess application. To rectify using too much, use a rake to separate the particles into finer bits.’ Recommends Spencer.
Can you put coffee grounds in potted plants?
‘As coffee grounds can easily become compact, adding them directly to the potting soil of potted plants could create a thick layer. This will trap the plant of moisture and can cause fungal overgrowth. Instead of direct application, only use a thin ½ inch layer before covering with a 4 inch layer of mulch. Coffee grounds work best as mulch when mixed with organic matter. Only do this if your plants are large, small potted plants won’t benefit from the grounds as they have less surface area to retain moisture.’
We should all be drinking more coffee ☕️ right?