As I sipped my morning coffee, surveying my garden, I pondered: are coffee grounds truly beneficial or harmful to our plants? In my line of work, I’ve learned that effective solutions aren’t always store-bought. Sometimes, it’s about repurposing what we have — like those used coffee grounds.
For us hands-on, environmentally conscious gardeners, exploring such methods is second nature. But remember, while coffee grounds might have their place, companies like Sunday Lawn Care offer tailored solutions for that picture-perfect lawn – minus the caffeine boost.
How Do Coffee Grounds Affect Plants?
Coffee grounds are organic matter containing various useful nutrients and trace minerals. When you add it to garden soil, it increases the number of micronutrients in the soil while improving its structure as well.
Washington State University identified the chemical composition of coffee grounds and considered it to be the nitrogen-rich proteins in coffee that contribute to enhanced soil composition.
It’s important for people new to gardening to understand that you’re not really impacting your “plants” per se. Right?
The addition of coffee grounds is designed to alter the soil, improve drainage, and attract helpful microorganisms to the ground where the plants are rooted.
What Are the Different Ways You Can Use Coffee Grounds In Your Garden?
Now that you know a little about the science behind coffee grounds in gardens, let’s think about some ways you can start collecting and using these grounds in your garden beds.
Compost
Compost is a mixture of incredibly nutrient-rich soil and other elements — like food scrap — that help provide nutrients to your plants as you grow them. The point of compost is to mix it in with your soil or potting mix to help your plants thrive and grow. If you’re planning to make compost, be sure to familiarize yourself with the guidelines for composting.
When and Why You Should Do This
Adding used coffee grounds to your compost bin helps improve the nutrient-dense soil and provides a better balance of nitrogen and carbon, which is necessary for decomposition.
Why is this important?
Decomposition will help break down some of the other items you have in your compost pile. This can include fruit and vegetable scraps, eggshells, plant cuttings, and grass clippings.
Add the coffee grounds to make a mixture that looks like soil. This will make a better compost and make the soil strong enough for your plants.
Tips for Not Harming Plants or Soil
- Mix coffee grounds thoroughly into your compost pile to prevent clumping.
- Use only used coffee grounds, as fresh coffee grounds can be too acidic. (Very important)
- Don’t rely solely on coffee grounds; mix them with other organic materials to create a well-balanced compost.
Fertilizer
For something to be considered a “fertilizer,” it needs to improve the productiveness of plant growth. This means that a lot of things can be fertilizer, not just the bags of Miracle-Gro you find at the local garden center.
Fertilizer contains three nutrients:
- Nitrogen
- Phosphorus
- Potassium
These three key minerals for plant growth are also found in coffee grounds, with the added bonus of calcium and magnesium.
Keep in mind, it’s not only useful for gardens but can help grow grass too.
You can use a top layer of coffee grounds as mulch too. Spread spent coffee grounds on the top layer of your flower beds to promote aeration and water retention.
When and Why You Should Do This
Coffee grounds are a great slow-release fertilizer because they don’t release all their nutrients at once, which is great for your plants.
You want to make sure to spread them around and don’t overdo it because of the acid in the grounds. If you add too much, it can lower your soil’s pH to dangerous levels. This leads to slow growth, yellow withered leaves, and excessive weed growth (explore some reliable ways of controlling weeds)
Tips for Not Harming Plants or Soil
- Only use a thin layer of coffee grounds (about half an inch) around your plants to prevent mold growth.
- Avoid applying coffee grounds directly to the base of plants, as this can cause root burn.
- Check the pH of your soil to ensure it doesn’t become too acidic.
Pest Control
One of the biggest issues I find homeowners struggling with is pests in their soil because they’re the “pests” you don’t always consider.
When you think of a pest, you usually imagine something above the ground, like a squirrel, rabbit, or various plant-eating bugs.
You’re not always thinking about slugs, snails, and ants.
When and Why You Should Do This
Coffee grounds serve as a natural repellent because of their strong odor. They also support some of the organisms you want around, like earthworms.
Vermicomposting in a worm bin is a great way to create compost that your plants will love.
Worms are important for breaking down your compost. If you have more worms in your garden, you won’t attract too many pests.
Tips for Not Harming Plants or Soil
- Use a light layer of coffee grounds around plants that are susceptible to pests.
- Refresh the coffee grounds as needed, as they can lose their effectiveness over time.
- Avoid using coffee grounds as the sole method of pest control — combine them with other natural deterrents for best results.
Which Plants Benefit the Most from Coffee Grounds?
Do you have a favorite plant you’re trying to grow but struggling to get it going? Perhaps your entire garden is in shambles?
Either way, don’t stress. Coffee grounds are pretty versatile and can be used on many plants.
Here’s a look at the plants that will benefit the most.
Hydrangea
Your hydrangeas do well in mostly acidic soil, so this is why coffee grounds are such a powerhouse for them. The higher the pH, the brighter your flowers will become.
That said, not everyone is looking for bright pink and red. If you’re trying to get a deeper blue or purple color out of your hydrangeas, introducing coffee grounds to the soil will lower the pH, causing a deeper and darker color flower.
Best Way to Use Coffee Grounds With Hydrangeas
- Spread coffee grounds evenly around the soil.
- Make sure to only introduce the grounds to established seedlings to prevent burning the sprouts.
Azaleas
Your azaleas are lush and they really help fill out the garden with bright, flowering shrubs. Depending on where you live, these plants might be either deciduous or evergreen.
They’re sensitive to pests and, even in the best conditions, can become very fragile to drought and overwatering.
Best Way to Use Coffee Grounds With Azaleas
- Don’t overfeed; these plants do not need a lot of nutrients.
- Check pH levels to around 5–6 for optimal growth.
Lily of the Valley
This plant is known for its bell-shaped bloom and strong aroma. It’s actually the inspiration behind one of the most popular perfume scents.
Lilies of the valley do better in mild climates and prefer a little shade — that’s why their blooms typically dangle to protect the flowering nectar from direct sunlight.
Best Way To Use Coffee Grounds With Lily of the Valley
- Use older coffee grounds to reduce the amount of acid in them.
- Spread coffee grounds evenly and be careful not to overdo it.
Carrots
Carrots do best in neutral soil, but they require a lot of drainage. Since they’re root vegetables, they’re more susceptible to pests. This is where your coffee grounds come into play.
Best Way to Use Coffee Grounds With Carrots
- Spread coffee grounds with other brown compost material evenly with the intention of preventing pests.
- Plant other acid-loving plants nearby to prompt optimal soil composition.
Radishes
Who doesn’t love a good radish? These globular root vegetables are known for being easy to grow and fast to sprout. They thrive well in warmer temperatures, and they go perfectly alongside carrots.
Best Way to Use Coffee Grounds With Radishes
- Add coffee grounds to the soil to increase the growth rate of the radish and surrounding plants.
- Spread coffee grounds to reduce pests.
Avoid Using Coffee Grounds on These Plants
Here are some plants that you’ll want to avoid spreading coffee grounds on or around:
- Tomatoes
- Peppers
- Eggplants
- Cucumbers
- Squash
- Melons
- Beans
- Peas
- Lettuce
What do they all have in common?
It all comes down to acidic soil. Coffee grounds automatically supply more acid to the ground, which can cause these plants to slow down, wilt, or even burn at the root.
While coffee grounds can’t help every plant, Sunday Lawn Care can certainly help get your yard up the par. Contact the company to see what safe ingredients its team uses on your lawn and garden.
How Should You Store Your Coffee Grounds for Gardening Use?
It’s important to properly store your coffee grounds to ensure they dry out and because they’re too acidic to use as soon as you brew a cup of coffee.
I recommend that you spread them out on a sheet of paper in a thin layer, so they dry out faster. Make sure you don’t store them until they’re fully dried because mold and fungus can grow, which will quickly become a hazard to your plants.
In fact, keep them in an airtight container in a dark, dry area until you’re ready to use them.
Read also: How to Boost Yard Drainage
Things to Consider
While coffee grounds can be beneficial for your garden, there are several important factors to keep in mind:
- Acidity levels: Fresh coffee grounds are acidic, but used coffee grounds are close to neutral. Always use spent coffee grounds in your garden to avoid altering soil pH too drastically.
- Application rate: Don’t overdo it. A thin layer of coffee grounds (about 1/2 inch) is sufficient. Too much can create a barrier that prevents water and air from reaching the soil.
- Nitrogen content: Coffee grounds are rich in nitrogen, which is great for leafy green growth. However, too much nitrogen can inhibit flowering and fruit production in some plants.
- Pest deterrent vs. attractant: While coffee grounds may deter some pests like slugs and snails, they can attract others like fungi and mushrooms.
- Caffeine content: Even in used coffee grounds, there’s still some caffeine present. This can inhibit seed germination and growth in some plants.
- Soil structure: Coffee grounds can improve soil structure, but they need to be mixed in well. If left in clumps on the surface, they can become hydrophobic and repel water.
- Plant specificity: Not all plants benefit from coffee grounds. Acid-loving plants like blueberries, azaleas, and rhododendrons tend to do well, while others may suffer.
- Composting first: Consider composting your coffee grounds before adding them directly to your garden. This can help balance out some of the potential negative effects.
- Water retention: Coffee grounds can help soil retain moisture, but this can also lead to overwatering if you’re not careful.
- Organic matter source: Remember that coffee grounds are just one source of organic matter. A diverse mix of organic materials in your soil is always best for overall garden health.
By keeping these considerations in mind, you can more effectively use coffee grounds to benefit your garden while avoiding potential pitfalls.
Frequently Asked Questions
Do avocados like coffee grounds?
Yes, avocado trees can benefit from coffee grounds. Avocados prefer slightly acidic soil with a pH between 6.0 and 6.5, and coffee grounds can help maintain this acidity.
However, use them sparingly and as part of a balanced fertilizer regimen. Mix the grounds into the soil around the tree’s drip line, or add them to your compost before applying.
Is there any point in dumping my coffee grounds directly on my garden soil?
While it’s tempting to simply dump coffee grounds directly onto your garden soil, it’s not the most effective method. Coffee grounds can form a barrier on top of the soil, preventing water and air from reaching plant roots. Instead:
- Mix the grounds into the top few inches of soil.
- Add them to your compost pile first.
- Use them as a thin mulch layer (no more than 1/2 inch thick).
These methods will help you gain the benefits of coffee grounds while avoiding potential issues.
Can I just go get used coffee grounds from coffee shops for my garden and compost?
Absolutely! Many coffee shops are happy to give away their used coffee grounds for free. This is an excellent way to obtain a large quantity of grounds for your garden or compost. Some tips:
- Call ahead to check if they participate in such a program.
- Bring your own container to collect the grounds.
- Be prepared for the grounds to be wet and heavy.
- Use these grounds just as you would use your own – in compost, as mulch, or mixed into the soil.
Do coffee grounds deter slugs?
Coffee grounds can help prevent slugs to some extent. The grounds’ abrasive texture can be uncomfortable for slugs to crawl over. Additionally, the caffeine content in coffee grounds may repel or even kill slugs. However, coffee grounds alone may not be a complete solution to a slug problem. For best results:
- Create a barrier around vulnerable plants with a thick line of coffee grounds.
- Combine coffee grounds with other slug deterrents like eggshells or diatomaceous earth.
- Reapply after rain, as wet coffee grounds lose their abrasiveness.
What is the best way to add coffee grounds to a vegetable garden?
The best way to add coffee grounds to your vegetable garden depends on your specific needs and the types of vegetables you’re growing. Here are some effective methods:
- Compost first: Add coffee grounds to your compost pile and let them break down before adding to your garden. This balances out the nitrogen content and reduces the risk of burning plants.
- Side dressing: Sprinkle a thin layer of coffee grounds around plants, keeping them away from the stem. Then, lightly work them into the top inch of soil.
- Soil amendment: Mix coffee grounds into the soil before planting. This can improve soil structure and add nutrients.
- Liquid fertilizer: Steep coffee grounds in water for a few days to make a liquid fertilizer. Dilute this “coffee tea” before applying to plants.
- Mulch: Use a thin layer (no more than 1/2 inch) of coffee grounds as mulch around acid-loving vegetables like carrots and radishes.
Remember, not all vegetables benefit from coffee grounds. Avoid using them around plants that prefer neutral to alkaline soil, such as tomatoes, peppers, and beans. Always monitor your plants’ health and adjust your use of coffee grounds accordingly.
Final Thoughts on Using Coffee Grounds in Your Garden
Coffee grounds can be a good addition to your garden if you use them correctly. They give your soil needed nutrients, make it better, and stop pests from coming in.
However, it’s essential to be mindful of their potential drawbacks and apply them properly to prevent any harm to your plants.
I’ve seen many homeowners implement coffee grounds into their gardens with much success, so as long as you follow the rules outlined in this guide, you should be no exception.
I highly recommend that you refer to our comprehensive basic guide on fertilizer application. This resource provides a wealth of valuable information to help you make informed decisions about fertilizing your lawn or garden. My guide covers the basics you need for successful and healthy plant growth. It includes understanding when to water and choosing the right fertilizer for your needs.
If you’re looking for the best option to breathe life into your plants and garden, Sunday Lawn Care may be able to wake them up more than coffee grounds can. Click the link below to get a free, no-obligation quote.
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