Do you throw coffee grounds away? Not anymore! Coffee grounds have many uses that can boost your garden and flower beds, just like it gives you a boost when you drink the coffee itself!
Composting coffee grounds not only reduces what goes to the landfill, it also benefits your plants. After reading this, will you still throw your coffee grinds away?
Used Coffee Grounds in the garden
Used coffee grounds can have many purposes in your garden. On top of recycling your coffee grounds in the garden, you will actually make plants thrive!
Coffee grounds for fertilizer
Not many of us have a compost pile or find the time to do proper composting. So go ahead and simply put coffee grounds directly into the soil!
It will not add nitrogen to the soil immediately. In the first phase, coffee grounds add organic material to the soil. This enhances drainage, aeration, and water retention.
Moreover, coffee grounds increase growth of microorganisms and earthworms.
- If you are into vermicomposting, coffee grounds can be used as worm food.
In a second phase, nutrients contained in the coffee grounds are released by microorganisms as they break it down. A whole line of microscopic fungus degrades organic material into plant-size bites.
You can also make coffee ground tea which is an excellent additive to make orchid fertilizer.
- fill half a pail with used grounds
- fill the pail to the top with water (soft water if possible)
- let sit for 24 hours
- filter out and discard the grounds to the compost, keeping nutrient-rich coffee grounds tea
Add one part ground coffee juice to three parts soft water, use it once a month during the growing phase. Keep in the fridge in a closed jar or bottle.
- Add coffee grounds to batches of fermented weed tea. It will leach nutrients into the mix!
Coffee grounds for mulch
Spreading layers of coffee grounds as mulch is beneficial when in lower quantity. Coffee grounds shouldn’t exceed more than 25% (one-fourth) of the mulch mix.
- Never layer the coffee grounds pure in a thick layer.
- The fine particles, when they dry out, form a watertight barrier. Only heavy rains and day-long drizzles soften it enough that water will reach the ground underneath.
- Always add other materials like river sand, compost and regular garden soil to make a balanced mix.
- Alternatively, let the grounds dry. This makes them easy to sprinkle on the ground in a thin layer.
Additionally, excess traces of caffeine from the ground coffee might have detrimental effects on some plants. If there are too much coffee grounds in the soil, plants will grow slower or stunted until such a time that soil organisms are able to break the coffee down.
- This is especially true for seedlings, when only pure coffee grounds are used.
- Coffee grounds will not kill grown plants. It just takes time for them to recover in case of excess amounts.
Coffee grounds for soil mix
As long as you keep the portion of coffee grounds below one-fourth (25%), you can mix coffee grounds with potting soil mix.
You can use this coffee-enriched soil mix to:
- prepare seedlings in trays,
- re-pot your plants,
- transplant seedlings and plants around your garden,
- prepare soil for planting trees and shrubs,
- topdress large pots and plants.
- again, for orchids, you can incorporate coffee grounds to the growing substrate. It has excellent drainage.
Note that if you add coffee grounds to seeding soil mix, be sure to add a spoonful of grated charcoal, too. Indeed, the high-nitrogen coffee grounds really support growth of fungus. For beneficial fungus, this is excellent, but when starting seeds you’d want to inhibit damping fungus instead.
Garden pests – coffee grounds keep ants, rabbits, slugs and snails away
Since caffeine has a negative effects on pests, it’s possible to use coffee grounds to protect your favorite plants from being eaten.
Typically, sprinkle the dried coffee grounds around areas you want to keep pest-free. Layering it on an ant hill will make the colony move out.
- Note: as with most repellents, it helps to provide “decoy plants” that will attract the pests, too. A good example of this is planting nasturtium to lure aphids away from your roses and other favored plants. Learn more on Nasturtium vs Aphids
Coffee grounds as a cat repellent
It seems cats do not like coffee grounds. If cats come in your garden to poo, you might want to try spreading some around!
- The strong scent makes cats feel their favorite spots for “number 2” are already contaminated.
Used coffee grounds to topdress a lawn
Coffee grounds have naturally high nitrogen content. This is particularly well-suited for grass.
- Used coffee grinds make for great lawn topdress.
- Apply directly, no need to mix it with other materials.
Coffee grounds to grow mushrooms
If you are into growing mushrooms, coffee grounds are also used as substrate for these fungus organisms.
The grounds are still full of nutrients which you can use to grow mushrooms, especially oyster mushrooms which love to grow on used coffee grounds.
With coffee grounds, you will skip the expensive pasteurization process of the substrate. The brewing process does that. All you have to do is:
- mix the spawn in the coffee grounds
- watch your mushrooms grow!
As you use your own coffee waste and perhaps your neighbors’, this means you get your substrate and grow more of your food locally.
Fresh ground coffee
Fresh coffee grounds can also be used in your garden. This is ground coffee that hasn’t been used to make a drink. Sometimes older coffee loses its savor and must be thrown away. Use it in the garden!
- Just remember that fresh coffee grounds are acidic whereas used coffee grounds are neutral.
- Indeed, making coffee transfers the acid to the drink, so used coffee grinds aren’t acidic anymore.
Although it isn’t a recommended practice for most plants, it is, however, favorable in some respects:
Fresh ground coffee is good for acid-loving plants
You can add fresh coffee grounds around plants like:
- Tomato, on the other hand, doesn’t grow well when coffee grounds are added in the soil.
Fresh ground coffee to suppress weeds
Weeds that grow around plants – especially those with allelopathic properties – can be minimized by using fresh coffee grounds. However, this should be used with a lot of care. As you suppress weeds, you might be also suppressing some beneficial fungal microorganisms.
Deter pests and other animals with fresh coffee grounds
Like used coffee grounds, fresh coffee grounds discourage pests and animals from coming to your plants and in your garden in general.
How do coffee grounds benefit the garden?
Why coffee grounds are good for soil
Coffee grounds, both used and fresh, have about 2% nitrogen. This is beneficial when added to your compost.
The C/N (carbon-nitrogen ratio) for roasted coffee grounds is 20, or about 20 parts carbon to one part nitrogen. For used coffee grounds, any water you put in the filter while making coffee also removes acidity. This ensures that used coffee grounds have a neutral pH level of 6.5 to 6.8.
Can I put coffee filters in the soil or compost pile?
Whereas the coffee grounds themselves are green compost material, coffee filters are also interesting and are brown compost material. Simply throw them in your compost.
You can also use coffee contained in special aluminum capsules and the like. Simply open them up with a knife on a cutting board and collect the grounds in a bowl or pail.
Coffee grounds are risk-free
Coffee grounds, since they go through the process of roasting, are always “healthy material” for composting and growing beds.
Unlike some store-bought fruits and vegetables, coffee is rarely treated with pesticides and chemicals. It can thus be used without fear of contaminating your garden soil with chemical products.
- In the case of flavored coffee beans, however, additives are also part of the mix. Check to see if the flavor is a natural extract or if it’s synthetic.
- Whether flavoring breaks down in a harmful way or not hasn’t yet been extensively studied.
Where to find coffee grounds for a garden
When you make a cup of coffee, what you consume is less than 1%. The other 99% of the biomass of the coffee is waste.
Even small gardens can absorb large amounts of coffee grounds.
Large providers of coffee grounds
- Check with coffee shops in your area. Some franchises already prepare packs of used coffee grounds for customers to take away.
- Restaurants often have coffee machines that produce quite a lot of coffee grounds.
You’ll notice that when asked politely (and not during rush hour!), many eatery managers will be happy to set some coffee grounds aside for you.
- Make it even easier for them: bring a container that closes with a lid, such as a large plasticware or a bucket with a lid.
- Agree on a schedule, and stick to it. Dispose of the coffee grounds quickly, or they’ll start molding within three to four days. This is why growing mushrooms on coffee grounds is perfect!
- Having two containers makes it easy to swap an empty one for the full one.
Neighborhood & community sources
Many families brew coffee every day. Even small capsules add up! An average coffee-drinking family will produce over a gallon of coffee grounds a month.
- Get together with neighbors. If they don’t want to use the grounds themselves, they’ll certainly be happy to keep them for you!
- Why not set up a community compost? Coffee grounds are perfect “compost material” that there can never be too much of.
Smart Tip for Used Coffee Grounds
Some people add used coffee grounds in their mushroom soil substrate.
Using coffee grounds in the garden on social media
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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Coffee grounds for the garden (also on social media) by Rosalyn & Gaspard Lorthiois, own work
Milling coffee by Rosalyn & Gaspard Lorthiois, own work
Coffee grains, roasted by Rosalyn & Gaspard Lorthiois, own work
Coffee basin (also on social media) by Rosalyn & Gaspard Lorthiois, own work