The Benefits of Coffee Grounds for Gardens
Reusing used coffee grounds for plants isn’t what most people have in mind when they pour a cup of steaming hot java. However, it’s a great alternative to just throwing grounds into the trash, especially when you consider how many cups of coffee are consumed each year.
When used properly, the dregs left after brewing can give your plants a nutrient boost as they contain nitrogen and micronutrients, which are absorbed through the soil. However, before adding coffee to your garden, test your soil to see if it’s actually lacking in any nutrients. Too much of a good thing can harm your plants.
Composting, mulching, and using coffee grounds as a fertilizer additive are all ways you can use coffee dregs to bring the best of your garden. Just be sure your plants will appreciate the effort — some species can be damaged by coffee.
The coffee for gardens topics we cover here include:
Facts About Coffee Grounds
First, some basics about coffee grounds. Despite popular belief, the Oregon State University notes that used dregs are not especially acidic. They’re actually closer to a neutral pH and range from 6.5 to 6.8. By volume, coffee grounds are about two percent nitrogen. Worried about those dregs going bad? They don’t. You can save them as long as needed.
Besides nitrogen, used coffee grounds include other nutrients such as calcium, phosphorus, iron, potassium, and magnesium. Coffee dregs may also absorb certain heavy metals that would otherwise contaminate the soil.
Each year, billions of pounds of java are consumed around the world. That adds up to a lot of waste going into landfills, so many people are interested in recycling or reusing leftover grounds. Putting used grounds to good use in a garden is one solution.
How To Use Coffee Grounds in the Garden
So what can you do with those last dregs of coffee after you’ve enjoyed a cup of joe? Plenty! When coffee grounds are used properly, your garden will appreciate them.
A quick explanation of composting is that it’s a way to recycle organic material. When exposed to air, certain solid materials like food and grass will gradually decompose over time into a thick substance called compost. Coffee compost makes a great fertilizer for plants. Composting can be done within a dedicated container, or it can simply be a pile in your yard.
Composting is not a quick process; it takes a minimum of four weeks for decomposition to occur, or even longer for some materials. Decomposition is a chemical reaction that releases heat during hot composting, so the temperature of the composting pile increases. Cold composting doesn’t have dramatically higher temperatures, so decomposition takes much longer.
Composting is the simplest way to use ground coffee for gardens, just toss dregs into your compost pile and forget about them. As previously mentioned, used dregs contain nitrogen, which makes them a green compost material. With composting, green materials must be balanced with brown materials to maintain the right temperature and speed of decomposition.
Leftover grounds will increase the nitrogen level in your compost pile, use grounds to make up 10 to 20 percent of your total compost pile only. However, a 4:1 ratio of brown material to green material should be maintained for proper balance, so don’t forget about things like leaves, newspaper, and wood chips. Paper filters also fall into the brown category but be wary as some may contain chemicals.
Coffee grounds make for an excellent mulch material in your garden. Since used grounds can improve soil’s ability to hold water, they’re a good choice. However, they should not be used as the only mulch. Used grounds may lock together, which can prevent water or nutrients from reaching the plants’ roots.
To prevent that, mix grounds into compost, leaf mold, or other materials that function as a mulch. You can also rake grounds into the top few inches of topsoil to ensure that grounds are scattered and not clumped together. You should avoid using coffee grounds around seeds or young plants as caffeine may interfere with their growth.
Weed and Pest Control
Anecdotally at least, dregs from java may help kill weeds and keep some pests away from your garden. Since most used grounds still contain caffeine and caffeine can inhibit plant growth, coffee grounds can help block weeds from growing in certain areas. However, make sure your own plants aren’t sensitive to caffeine beforehand.
There’s no hard evidence that leftover grounds will protect your plants from pests who nibble on them, but many people swear by it. Coffee grounds have a very abrasive texture, so that combined with caffeine content may be enough to deter snails and slugs from your garden. Grounds can also make your garden unattractive to cats, who are known for using gardens as personal litter boxes.
While coffee grounds can be beneficial when included with fertilizer, coffee grounds don’t work as fertilizer on their own. They may be used to add nitrogen to compost, which can then be used as fertilizer, but grounds won’t directly add nitrogen to your soil. However, used grounds do add organic material to the soil, which can benefit your garden.
You can also make a liquid spray for gardens with used ground coffee. Take two cups of used grounds and add them to five gallons of water and steep for 12 hours. You can then spray this liquid on your coffee-approved plants. It may help the soil while also acting as plant food. Again, just make sure your plants are species that like java!
Plants That Like Coffee
So which plants like used coffee grounds? Typically, coffee-loving plants like high-acid soil and can handle extra nitrogen. The most common plants you can safely give leftover grounds to include:
- Azaleas, along with other plants in the rhododendrons genus
Plants Coffee May Harm
On the other hand, there are some plants that do not appreciate coffee grounds in their gardens. Using leftover dregs with these plants may stunt their growth and even kill them. Aside from specific plants, you shouldn’t use grounds on soil that already has high nitrogen levels. This is also why you should test the soil before using dregs from java, or any kind of fertilizer, really.
Some specific plants that can be negatively affected by leftover grounds:
- Chinese mustard
- Asparagus ferns
Other Considerations With Using Coffee
As already suggested, there can be some negative effects from using coffee grounds in your garden. Because coffee dregs contain nitrogen, they may lead to too much nitrogen in the soil, which can damage your garden. Any caffeine present in used grounds can also negatively impact some plants, particularly young ones, seeds, or seedlings.
In addition, coffee grounds can harm some pets if ingested. Most cats will simply ignore them, but dogs may try to eat grounds or dig into the soil where grounds have been sprinkled in, and caffeine is toxic to dogs. So if you have a pet who wanders through your garden, it’s probably a good idea to steer clear of using leftover grounds.
The hidden benefits of java include the coffee grounds themselves, which can definitely have an impact on your garden. But it’s important to understand what you’re dealing with before you start sprinkling those coffee dregs. Test your soil so you can determine its pH level and what, if any, nutrients are missing. Verify that your plants can handle coffee grounds so you don’t end up accidentally killing any.
Are coffee grounds good for plants and trees? When used appropriately, coffee grounds can be a great addition to compost piles, mulch, or fertilizers. Leftover grounds are organic matter, which may help the soil retain water and nutrients better, which may promote plant growth.
So the next time you finish that cup of joe, don’t toss those coffee dregs in a trashcan. Save them for your best gardening practices.
Are Coffee Grounds Good for Plants? FAQs
Can You Put Too Much Coffee Grounds in Your Garden?
As a matter of fact, yes. Coffee grounds contain nitrogen, and if you add them to soil that’s already nitrogen-rich, it may cause harm to your garden.
Can You Put Coffee Grounds in Houseplants?
Yes, but only certain types of plants will appreciate it. For example, African violets and jade plants respond well to grounds. However, plants that are sensitive to caffeine should not be exposed to coffee.
What Can I Do With Old Coffee Grounds?
So many things! You can do everything from sprinkling them in your garden to using them as a skin exfoliator. There are multiple uses for coffee grounds in the garden, which we’ve covered in more detail above.
Do Coffee Grounds Kill Ants?
Probably not, but coffee grounds may deter ants and block them from coming closer to your beds or your home.
Are Coffee Grounds Good Fertilizer?
Coffee grounds should not be considered fertilizer by themselves. They contain nitrogen, but that nitrogen doesn’t directly transfer to soil around the grounds. However, they can be added to fertilizer mixes, where their organic characteristics will help soil better retain water and nutrients.
Which Plants Benefit from Coffee Grounds?
Plants that love nitrogen and acidic soil respond well to used grounds. These plants include hydrangeas, blueberries, and azaleas.