Whether you’ve tried coffee grounds in your garden before, you might wonder if you’re hurting or helping yourself.
It’s important to understand that the best things for your garden aren’t always on a hardware store shelf. Sometimes you need to get creative, and putting used coffee grounds in gardens is popular for several reasons.
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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 overall structure as well.
A study performed by 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 we understand a little about the science behind coffee grounds in gardens, let’s consider some applicable 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 enhance 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.
By adding the coffee grounds, you’re helping to break all of these ingredients down to create a more soil-like mixture that will provide a better compost while also ensuring the soil structure is strong enough to support 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.
- Monitor 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 essential for the breakdown process of your compost, and if you have a higher population of worms in your garden, you’ll decrease the chances of attracting 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 deterring 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.
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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
Our Take: Should You Start Using Coffee Grounds In Your Garden?
When used correctly, coffee grounds can be a valuable addition to your garden, providing essential nutrients, improving soil quality, and acting as a natural pest deterrent.
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.
We 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. From understanding the right timing to selecting the appropriate fertilizer for your specific needs, our guide covers the fundamentals you need for successful and healthy plant growth
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.
