How to reuse coffee grounds to help your garden grow

How do I do this, we hear you ask?

Well, here to help is Cafédirect, which has teamed up with expert coffee farmer Joel Silva Arrascue, a member of the Prosperidad de Chirinos cooperative, which Cafédirect has partnered with since 1991.

Below, is the inside scoop on the genius ways Joel and his cooperative repurpose coffee waste to boost their crop yields - from creating high-quality organic fertiliserandbait traps for pests. So gardeners can take note too.

Based in Peru, Joel has been a part of the cooperative for two years, farming award-winning Cafédirect coffee at an altitude of 1,900 meters. As a social enterprise and Fairtrade coffee company that exists to protect the future of coffee by putting people and the planet first, Cafédirect works with its cooperatives to maximise sustainability.

They use coffee production by-products to create organic fertilisers—transforming coffee grounds into valuable nutrients for their plants.

Why is coffee good for plants?

Coffee is packed with beneficial nutrients like nitrogen, potassium, and phosphorus, key ingredients for healthy plant growth. This is because nitrogen helps plants produce chlorophyll, which means they can capture sunlight, and so supports their growth.

Potassium strengthens roots and helps plants withstand stress, while phosphorus is essential for healthy root development and supports the blooming of flowers and the growth of fruits.

When used correctly, coffee grounds can significantly improve your soil quality. The key is knowing which plants will be the ones to benefit!

Which plants should I use coffee grounds on - and which to avoid?

Usecoffee grounds to help fertilise acidic-loving plants such as azaleas, hydrangeas, rhododendrons, and roses. They can also help to boost vegetable crops like carrots, cucumbers, peppers, potatoes, and radishes.

Top tip - always mix the coffee grounds into the soil rather than just scattering them on top. This is because laying them on the surface can cause a crust to form, which stops water from penetrating the soil and reaching the roots.

Avoid using them on plants that prefer alkaline soil, like lilacs, lavender, and certain herbs and geraniums - as the slight acidity may be harmful.

Making organic soil feed

DIY fertilisers are a great way to feed plants directly when they suffer from nutrient deficiencies. They can be made at home and applied directly to the soil around the base of the plant to enrich the soil and feed the roots. An insider tip is to avoid putting the fertiliser straight on the leaves though, as the ingredients could damage them.

Joel and his cooperative create an organic fertilizer by mixing coffee grounds with ash and crushed eggshells. This becomes a nutritious and effective concoction which works wonders to balance pH levels.

The coffee farmers at Cafédirect apply this nutrient-rich mixture to their crops, including coffee plants, flowers, cassava, and fruit trees. Joel said: “Our organic mix has helped us to see pH levels drop from 3.2 to around 3, which really helps us naturally fight off plant diseases.”

How to create a fertiliser with coffee grounds

For those who want their morning coffee to do more than just wake you up, mix together:

• 90g used coffee grounds
• 60g wood ash (from a fireplace, fire pit, outdoor bonfire or wood-burning stove)
• 30g finely crushed eggshells (about three to four eggs worth)
• 2 litres water

Instructions:

• Step 1: Mix together your used coffee grounds, wood ash, and crushed eggshells in a large bucket or container
• Step 2: Add the water and stir thoroughly (your mixture should look earthy and loose)
• Step 3: Leave it to soak for 24 hours. This will allow nutrients to leach into the water
• Step 4: Give it another good stir
• Step 5: Pour your homemade fertiliser directly at the base of your plants (making sure to avoid the leaves), or strain if you’re using a watering can

There you have it, your very own eco-friendly, DIY coffee ground fertiliser to nourish poorly plants! It’s ideal for veggies, flowers, potted plants, and even fruit trees (in moderation) and can be applied every 2–4 weeks during the growing season. Store any leftovers in a sealed container - making sure to give it a good stir before each use.

How to make wood ash at home

If you plan to make the wood ash yourself at home, here are four simple steps:

Step 1: start by burning your wood

• Use a fireplace, wood-burning stove, fire pit, or outdoor bonfire
• The wood itself needs to be clean, untreated, unpainted and natural. Hardwoods produce better-quality ash (think oak, maple, and ash)
• Avoid painted or varnished wood, charcoal briquettes (which often contain additives) and pressure-treated lumber

Step 2: Let the fire burn down completely

• Patience is a virtue. Wait until the wood has turned to a white-grey ash. You want there to be little to no black charcoal left

Step 3: Let the ash cool fully

• You need to give the ash at least 24 hours to cool down and settle before handling it. Hot ash can stay dangerous longer than you think!

Step 4: Collect the ash

• Make sure to use a small shovel or a metal scoop to avoid contact with your hands
• Sift through to remove any large unburned chunks or debris
• Exposure to moisture will make the wood ash clump - which reduced its effectiveness - so store it away in a dry, sealed container (an old coffee tin or lidded bucket will do the trick)

How to get your hands on wood ash

If you don’t have a fireplace and are wondering where you can source wood ash, here are some alternative options:

• Ask friends or neighbours with a wood stove or fireplace if they might be happy to share
• Pop into your local pizza place or craft bakery, as they sometimes give ash away
• In rural or allotment communities, you’ll often find folks with regular bonfires or burn piles, so its worth asking around
• Take a trip to the garden centre, as they tend to offer wood ash (just make sure to check that it’s clean and chemical-free)
• Check with online gardening forums

How to use coffee grounds to repel slugs and snails

One of the most common uses of coffee by-products for farmers like Joel is as pest traps, such as for the coffee borer beetle. This is one of the most destructive pests for coffee plants, as it burrows into the coffee cherries and damages the beans, so managing this pesky beetle is crucial to maintaining healthy coffee crops.

If pests like slugs and snails are causing chaos in your garden, why not be inspired by the coffee farming pros and try sprinkling coffee grounds around the bases of your plants? Slugs and snails aren’t fans of coffee, so this simple trick can act as a natural repellent to help keep them at bay.