Coffee Grounds For Plants To Make Them Thrive

If you’re looking for natural ways to get rid of pests on your plants or are just curious about how to compost using coffee grounds, consider reusing your used coffee grounds for plants. They can be an effective and eco-friendly solution for both pest control and soil enrichment.

Doug Oster, gardening author and co-host of The Organic Gardener radio show, recommends adding coffee grounds to your gardening routine, saying, “It is easy to get, it breaks down quickly, and like all living matter, it will compost.”

Incorporating recycled coffee grounds as fertilizer for your plants is not only environmentally friendly but also a simple means of reducing waste and enhancing plant growth. Whether you have a small indoor garden or a large backyard plot, coffee grounds can prove to be a useful addition, provided they are utilized correctly.

Benefits of Coffee Grounds for Gardening

There are many benefits of using coffee grounds for gardening.

• Using coffee grounds for plants improves the soil and reduces landfill waste.
• Simply tilling used grounds into the soil can help with aeration, drainage and water retention.
• Coffee grounds add vital nitrogen to the soil that allows plants to absorb water and nutrients, like using wood ash in the garden.

It doesn’t matter if you drink decaf or regular—either will do the trick. As for the format, used coffee grounds are the gold standard, as the acidity in the grounds is neutralized after brewing, although some plants can handle grounds that haven’t been brewed.

As for indoor plants, a teaspoon of spent coffee grounds mixed into the soil can work for most. Super-diluted coffee dregs can even be used for occasional watering. However, grounds help with water retention, so you must be careful with succulents and plants that like dry soil. Too much moisture from coffee grounds can lead to root rot.

Which Plants Are Coffee Grounds Good For?

Both indoor and outdoor plants can benefit from a Java boost, but that doesn’t mean you can take a one-size-fits-all approach to coffee in your garden. For best results, use the type of grounds that best suit your plants.

Coffee that has already been brewed works best for the garden, says Sonia Uyterhoeven, head of horticulture at New Jersey’s Greenwood Gardens. “When you make coffee, all acidity gets washed out,” she says. That means it won’t change the pH level in your garden. You can blend used grounds into the soil throughout the garden. But she prefers adding it to compost, which is better garden food overall.

Coffee that has been roasted but never brewed is fine for acid-loving plants, including rhododendrons, azaleas, hydrangeas, Pieris andromeda and camellia. Uyterhoeven suggests sprinkling those grounds in a thin layer around a bed of acid-loving plants, along with a layer of mulch.

Oster recommends composted coffee grounds only for vegetable gardens. Coffee can contribute to an acidic environment that blueberries benefit from. Higher nitrogen would also help spinach, lettuce, arugula and mustard greens.

Which Plants Do Not React Well to Coffee Grounds?

Not all plants are receptive to soil mixed with used coffee grounds. Take your vegetable garden. If you grow your own food and want yours to thrive, avoid adding coffee grounds directly to it. For growing vegetables like tomatoes or lettuce, Oster recommends using plant-specific fertilizers, well-rotted manure or balanced compost. Coffee grounds may also deter seedlings, so skip them in areas where you’ve started plants from seed. Other plants that don’t love the leftovers from your morning brew? Weeds—and that’s a good thing. Experiment in areas where weeds self-sow and thrive. The grounds could be your best-smelling, organic weed deterrent!

We recommend being cautious and checking your plants’ requirements before using coffee grounds as organic waste for soil enrichment to grow your plants.

How Do You Use Coffee Grounds for Plants?

If you want to add your coffee grounds directly to plants, remember those rules about acidity. For hydrangeas and azaleas, it’s fine to add a thin layer around the plants themselves. Even a leftover bag of ground coffee that hasn’t been brewed can work. Just try to avoid a solid mass of coffee grounds, since that could block water.

How to compost with coffee grounds

Compost needs brown and green materials to work effectively. Despite their appearance, coffee grounds are considered “green”—that is, they add nitrogen.

Oster aims for a 50-50 mix of green materials and brown ingredients like newspaper and dry leaves. When he adds coffee grounds, he includes the paper filter (feel free to tear it into smaller pieces) and a layer of straw.

To use compost, wait until it’s completely decomposed. That can take months or years, depending on heat, ingredients, location and other variables. Spread it evenly in beds in early spring or at the end of the growing season. For new plantings, combine compost with existing soil.

Coffee grounds as fertilizer

While coffee grounds can change soil acidity and add nitrogen, using them directly as a fertilizer takes time. If the coffee has been brewed, the acidity has been neutralized.

Spent grounds can be lightly tilled into the soil or spread around throughout a planting bed. They will take longer to break down and release nitrogen, so add another fertilizer while the coffee decomposes in the soil.

Be smart about where you’re using coffee grounds. Remember, stick to plants and shrubs rather than veggies to avoid dead plants.

Coffee grounds for pest control

No one likes snails and slugs in the garden, and there is certainly no harm in trying to deter them with some used coffee granules. On their own or mixed with mulch, they will smell pretty good for a while. But despite the rumored benefit, horticulturists say coffee grounds are unlikely to attack the pest population already affecting the plants. It’s possible, however, that the grounds would prevent some garden pests from crossing an uncomfortably granular surface to a different area.

Coffee grounds to keep cats away from plants

Folklore also says cats are not fans of how coffee smells. While it’s tough to prove scientifically, it’s easy to experiment. Consider using decaffeinated coffee or spent grounds with less acidifying risk. Sprinkle them around the plants you want to protect. But beware, dog owners: avoid anything caffeinated that may reach your canine friends. Citrus scents are an alternative option for keeping pets away from the garden.

Coffee grounds to feed worms

Everything is better in moderation, and that goes for worms that love a good cup of joe. Vermicomposters—folks who compost using worms—swear the grounds are a favorite treat. Start with a small amount to see if the worms like it. If you use too much, your vermicompost could become too acidic.

Just how much should you use? Guidelines vary from about 15% of their diet to one-eighth of their bedding.

In the ground, compost naturally attracts worms that ostensibly like coffee as well. That’s a good thing, provided coffee is actually good for worms. However, a study published in Bioresource Technology suggests a higher mortality risk for earthworms exposed to coffee grounds in multiple composting methods.

The same study showed that adding cardboard lowered both the risk and chemical exposure, so gauge your comfort level.

Mistakes to Avoid When Using Coffee Grounds

Recycling used coffee grounds for plants isn’t complex, but you’ll have a better chance of success if you avoid the following missteps:

• Don’t use fresh unbrewed coffee grounds if your plants are not familiar to you. The brewing neutralizes the acidity in coffee, removing potential harm to plants that don’t like it. And as an economic matter, why waste coffee if you can brew it first and garden with it later?
• Coffee filters heading to compost should be unbleached to keep the fertilizer organic. The smaller the pieces, the faster the decomposition.
• Avoid chemically flavored coffee grounds.
• A solid layer of coffee grounds can hurt the garden more than it helps by preventing water from reaching the roots when you’re watering your plants. Instead, use it in compost or blend it into the soil.
• Compost coffee grounds for a vegetable garden instead of using them directly. Remember, coffee grounds are not good for tomatoes or seedlings.
• Get a soil test, especially if your plants are not thriving or you want to change the soil’s acidity. Most counties have a local Cooperative Extension Service eager to advise gardeners.

FAQ

Is it better to use wet or dry coffee grounds for plants?

Dry coffee grounds are recommended for gardening. Mix dried grounds into the soil to boost nitrogen and other nutrients. Sprinkle them around plants to help repel pests like slugs and snails. Add to compost to enhance the carbon-to-nitrogen balance and speed up decomposition.

About the Experts

• Doug Oster, garden book author and co-host of The Organic Gardener radio show, promotes using coffee grounds as a simple and effective way to enrich soil. He highlights their quick breakdown in compost and encourages pairing them with brown materials like straw for balance. Oster also advises brewing the coffee first to neutralize its acidity before using the grounds in gardening.
• Sonia Uyterhoeven, head of horticulture at Greenwood Gardens in New Jersey, recommends brewed coffee grounds for general garden use since the acidity is washed out. She suggests unbrewed grounds only for acid-loving plants like azaleas and hydrangeas. Uyterhoeven prefers adding grounds to compost to ensure optimal soil health.