Are Coffee Grounds Good for Plants? An Expert Weighs In

2024-04-23
Are Coffee Grounds Good for Plants? An Expert Weighs In

Are coffee grounds good for your plants? You might wonder this after hearing the advice to add coffee grounds to your garden soil and houseplants to help your plants thrive. Or maybe you've visited coffee shops that are giving away bags of their used grounds for customers to use in the garden. The idea is that coffee grounds act as a natural fertilizer and organic soil amendment. But do they really? We asked an expert to definitively sort out fact from fiction.

Chelsea McKinley is a plant health care specialist at the U.S. Botanic Garden in Washington, DC., where she has worked since 2014. She holds a B.S. in Environmental Horticulture Science.

Using Coffee Grounds for Plants

So are coffee grounds good for plants? The short answer is not really—at least not when you put them directly on your plants, says Chelsea McKinley, plant health care specialist at the U.S. Botanic Garden in Washington, DC.

That’s not to say used coffee grounds have no value to a gardener. They do, just not as fertilizer or a soil amendment. “The best way to use coffee grounds in gardening is to compost them,” McKinley says.

“You don’t get the full potential out of coffee grounds by mixing them into the soil,” she says. “You’ll get the full potential out of them if you properly compost them and then use that compost to fertilize your plants because then the nutrients are more readily available and in proportions more appropriate for plant growth.”

Coffee grounds are considered a "green" material when used in compost, based on their carbon to nitrogen ratio. Mix the grounds with two to three times as much "brown" materials in your compost bin to achieve the right balance for an efficient decomposition process. In a few months, all your grounds (you can throw in paper coffee filters too), along with dried leaves, grass clippings, and kitchen scraps, will turn into nutrient-rich compost that will benefit your plants.

Do Coffee Grounds Acidify Soil?

Another claim floating around the internet is that coffee grounds are a good soil amendment for acid-loving plants because they lower the soil pH, which is desirable for plants like azaleas, blueberries, and hydrangeas.

That’s not true, McKinley says. “Coffee grounds have a pH between 5.5 and 6.5,” she says. “Most plants like a soil pH between 5.8 and 6.8, so coffee grounds won’t lower the pH significantly.” It works about as well as mulching with pine bark.

If you want to lower your soil pH, use a fertilizer designed to lower soil pH, McKinley says. “That’s a faster way to acidify soil.”

Are Coffee Grounds Good for Houseplants?

While used coffee grounds contain a little nitrogen, an element that plants need to grow, the nitrogen isn’t in a form that’s easy for plants to use. Plus, it's easy to overdo it.

“If you add too many coffee grounds to your potted plant, it’s like overfertilizing them, and you burn the roots of the plant,” McKinley says. “Burned roots can lead to dead plants.” 

Potted plants are especially sensitive to dramatic changes in nutrient levels because they’re growing in an artificial environment with limited space, McKinley says. “I wouldn’t put coffee grounds on potted plants.”

Do Coffee Grounds Improve Soil?

It’s true that coffee grounds can improve soil structure when put directly into garden soil, McKinley says. Soil structure affects how much water and air move through the soil. Soil with good structure is well-drained and holds nutrients vital to plant health.

“If you have heavy clay soil, adding any organic amendment, even coffee grounds, can help,” she says. “Microbes in the soil will break down the coffee grounds eventually, but you’re not going to get the full potential from your coffee grounds unless you compost them.”

Frequently Asked Questions

  • Do some plants not like coffee grounds?

    Tomato plants and rhododendrons tend to respond poorly to direct exposure to coffee grounds, but using compost that contains coffee grounds causes no problems.

  • Can I use coffee grounds in the soil when I plant seeds?

    Coffee grounds inhibit the germination rates of some seeds while enhancing the germination rates of others. To stay safe, use compost that contains coffee grounds instead of direct coffee grounds.

Related Article

How to Grow and Care for Calathea

How to Grow and Care for Calathea

Learn how to grow calathea indoors successfully. This guide includes essential tips for watering, humidity, light, and fertilizing.
9 Common Houseplants You Might Not Know Are Poisonous

9 Common Houseplants You Might Not Know Are Poisonous

Many favorite houseplants are toxic if ingested, so be extra careful with them, especially around small children and pets.
8 Common Bird Feeder Mistakes You Might Be Making (And How to Fix Them)

8 Common Bird Feeder Mistakes You Might Be Making (And How to Fix Them)

When keeping bird feeders in garden areas, make sure to avoid these bird-feeding mistakes. Instead, keep your winged visitors healthy and happy year-round.
This Front Yard Prairie Garden Requires Almost No Maintenance

This Front Yard Prairie Garden Requires Almost No Maintenance

An Iowa gardener takes cues from nature to create an easy-care wildlife haven filled with colorful native plants.
How to Attract Fireflies to Your Yard for Delightful Evenings

How to Attract Fireflies to Your Yard for Delightful Evenings

Enjoy a natural light show by learning how to attract fireflies to your yard. These enchanting bugs are not only entertaining, but good for your yard.
How to Make a Pallet Potting Bench for Your Gardening Projects

How to Make a Pallet Potting Bench for Your Gardening Projects

Follow our step-by-step guide to make a beautiful and functional pallet potting bench using recycled wood pallets.
Hydrangeas Not Blooming? 7 Reasons Why and How to Fix the Problem

Hydrangeas Not Blooming? 7 Reasons Why and How to Fix the Problem

Hydrangeas not blooming can be a frustrating problem for gardeners. These straightforward tips will promote tons of long-lasting flowers.
Dress Up Your Home with This Foolproof Foundation Garden Plan

Dress Up Your Home with This Foolproof Foundation Garden Plan

Create a welcoming look for your home with this easy-care combination of foundation plantings that will look great around the foundation of your home.
This Extra-Easy Sun-Loving Garden Plan Blooms for Months

This Extra-Easy Sun-Loving Garden Plan Blooms for Months

Try this extra-easy sun-loving garden plan to enjoy tons of color from tough perennials that don't require a lot of maintenance.
How to Plant and Grow Sword Fern

How to Plant and Grow Sword Fern

This guide provides essential tips on how to grow sword fern, a North American native with a big garden presence.
How to Make a Succulent Heart Planter from Concrete

How to Make a Succulent Heart Planter from Concrete

Cement your love of succulents by whipping up this adorable concrete planter that you can hang up.
11 Small Vegetable Garden Ideas for Maximizing Your Homegrown Harvest

11 Small Vegetable Garden Ideas for Maximizing Your Homegrown Harvest

These small vegetable garden ideas will help you make the most of the growing space you have.
Can You Plant Garlic in the Spring? With These Must-Know Tips, You Can

Can You Plant Garlic in the Spring? With These Must-Know Tips, You Can

Even if you missed the fall planting window, here's how you can plant garlic in spring and still get tasty greens and bulbs to eat.
When Should You Aerate Your Lawn to Grow Healthier Grass?

When Should You Aerate Your Lawn to Grow Healthier Grass?

Knowing exactly when you should aerate your lawn will help you revive a struggling lawn without chemicals. Here's how to tell if your lawn needs aerating and how to time it right.
What Is Grass Paint? Plus 6 Tips for Painting Your Lawn

What Is Grass Paint? Plus 6 Tips for Painting Your Lawn

A coat of easy-to-apply grass paint is a quick way to turn a brown lawn green. Get tips for when and how to use grass paint for a lush-looking lawn.
What You Need to Know About Winterizing a Lawn

What You Need to Know About Winterizing a Lawn

Get a jumpstart on a lush, healthy lawn next spring with this guide on winterizing a lawn. Plus, get your lawn mower ready for winter storage.
How to Create Organic Soil for Your Healthiest Garden Ever

How to Create Organic Soil for Your Healthiest Garden Ever

Turn sand, clay, or barren ground into rich, organic garden soil that will sustain plants for years with the right ingredients and these expert tips.
Peach Tree Diseases and Pests

Peach Tree Diseases and Pests

Here's what you need to know about common peach tree diseases and pests and how to fight them.
18 Backyard Landscaping Ideas to Upgrade Your Hangout Spots

18 Backyard Landscaping Ideas to Upgrade Your Hangout Spots

Use plants, hardscaping, and other backyard landscape design elements such as water features, fencing, and arbors to create privacy and beauty.
16 Front Yard Flower Bed Ideas for a Welcoming Entryway

16 Front Yard Flower Bed Ideas for a Welcoming Entryway

These front yard flower bed ideas will add curb appeal and welcome guests to your home through the seasons.