How Coffee Grounds Can Supercharge Your Plants

If you love gardening and have some extra coffee grounds around, you’ll be glad to know that those grounds can help boost your green thumb. Coffee grounds are really good for plants in some circumstances. They can easily be used for many reasons, from extra nourishment to pest control. Knowing how to incorporate them into your gardening routine is key to ensuring optimal plant and lawn health.

Whether you’ve been there and done that and are looking to enhance your current gardening regimen or are new to gardening and looking for the ground rules when using coffee beans, we’ve got you covered. Ahead, professors, horticulturists, master gardeners, and extension specialists weigh in on the nuances of the answer to the question “Are coffee grounds good for plants?” Additionally, they share best practices when it comes to using coffee grounds on different types of plants, lawns, and soils.

Are Coffee Grounds Good for Plants?

Coffee grounds can be good for plants depending on the type of coffee grounds used, the type of plant, and how the coffee grounds are used. That said, “There is a significant difference between fresh and used coffee grounds. Most of the nutritional benefits come from the fresh stuff, not the stuff you can get by the bucket from your local barista,” explains Jonathan Russell-Anelli, a senior lecturer and extension associate at Cornell University’s School of Integrative Plant Science.

Which plants are coffee grounds good for?

Although we’ve covered the basic answer to the question “Are coffee grounds good for plants?” it is important to know which plants (as only some prefer more acidic soil). Plants that benefit from coffee grounds include cabbage, soybeans, anthuriums as well as some other houseplants, root vegetables, and ericaceous plants such as azaleas and hydrangeas, adds Stephen Pryce Lea, the deputy executive director of horticulture at the Delaware Botanic Gardens.

What plants do not react well to coffee grounds?

As important as it is to know which plants react well to coffee grounds, it is equally important to be aware of the plants that may experience an adverse reaction. “Plants that prefer a more alkaline soil may not thrive as much with coffee grounds and may become stunted over time, ” explains Masterson. Barychko adds that these types of plants may also experience burns resulting from over-acidification, and nobody wants that. As far as specific plants go, Langelo notes that you should avoid placing coffee grounds on plants, including orchids, tomatoes, rosemary, lavender, cover, alfalfa, and century plants, to name a few.

Luke Gatiboni, Ph.D., a professor in the Department of Crop and Soil Sciences at North Carolina State University, recommends testing your soil and coffee grounds beforehand to avoid applying coffee grounds to plants that may not be as receptive to them or those already planted in acidic soil. Luckily for you, testing soil pH can easily be done using a strip kit or by sending your soil to a laboratory (although this might be a larger investment).

Are Coffee Grounds Good for the Lawn?

Daniel Barychko, a horticulturist at the Central Florida Zoo, notes that coffee grounds can be good for the lawn depending on how they’re used, the type of grass, and the soil pH. To be most favorable for a lawn, coffee grounds should be properly composted, explains Wendy Wilber, a Florida master gardener volunteer program coordinator and horticulture extension agent for the University of Florida IFAS. “[Coffee grounds] can be beneficial on lawns when used sparingly, improving soil health and providing a natural slow-release fertilizer,” adds Lea.

Coffee grounds can benefit the lawn by adding trace minerals such as nitrogen and phosphorus, adds Linda Langelo, a Colorado-based horticulturist and extension horticulture specialist at Colorado State University. However, you need to be careful to ensure your soil’s mineral levels are balanced to prevent the overuse or depletion of other trace minerals.

Why Are Coffee Grounds Good for Lawn/Plant Care?

According to Lea, “Coffee grounds add essential nutrients (such as nitrogen, potassium, and phosphorus) back into the soil naturally, improve the soil structure, and help foster a healthy ecosystem for beneficial microorganisms and earthworms. They can also help control pests without the need for chemical treatments.”

How To Use Coffee Grounds for Plants/the Lawn?

In compost

Composting coffee grounds is one of the most effective ways to use them when it comes to plant and lawn care, as many lawns cannot handle the large quantities of caffeine contained directly in coffee grounds themselves. “If using it [coffee grounds] as compost, you can make compost as quickly as your piles can be finished,” explains Irish-Hanson. With this in mind, she adds that you should aim to keep your concentration of coffee to 20% or less (with between 10% and 20% as the ideal range) in your compost to create the healthiest mix.

“At my home for the past two years, I have been adding all my coffee grounds and vegetable waste into a composter that dries the coffee grounds and vegetables and breaks them down,” says Andrea Masterson, a horticulturist and collections manager at The Buffalo and Erie County Botanical Gardens. “I store this compost until spring, then I add it to the soil in my vegetable garden. Last year was the first year I did it and I believe it was very beneficial and helped create a good yield.”

Adding them to a worm bin

Barychko notes that one of the most advantageous ways to use coffee grounds is as part of a worm bin. “The earthworms can consume the grounds, break them down and add the nutrients to their “castings” which forms a very rich and nutrient-dense soil amendment that is safe to use without the worry of burning your plants or grass,” he adds.

As fertilizer

Although it is not recommended that coffee grounds be used as your main fertilizer source, depending on the circumstances of the lawn, you might be able to occasionally use them as a slow-release fertilizer. Mixing coffee grounds with other organic matter is a best practice when it comes to fertilizing soil.

As a soil amendment

Although coffee grounds can be used as a soil amendment, it can become costly. Wilber notes that when you mix composted coffee grounds into garden soil, it will enhance the soil’s overall structure and ability to hold nutrients.

What Not To Do When Using Coffee Grounds as Lawn Care

If you plan on using coffee grounds as lawn care, there are a couple of things you want to avoid. First and foremost, Langelo notes that you should not apply them directly onto your lawn as their caffeine can harm the microbes within the soil. Barychko adds that you don’t want to over-apply coffee grounds (or apply them in clumps) to a lawn as this may cause over-acidification and your lawn to experience unwanted holes. It is also a best practice to avoid applying coffee grounds directly onto seedlings as their high nitrogen content can prevent younger plants from properly germinating and growing, explains Lea.

Can coffee grounds hurt my lawn?

“If used excessively, coffee grounds can hurt your lawn as adding too much coffee grounds to your soil can create a compacted coffee layer, reducing air and water flow in the soil, leading to root suffocation and potentially harmful mold growth,” explains Lea.

How often should I use coffee grounds in my plants and lawn?

How often you should use coffee grounds in your plants and lawn will depend on several factors, including how you decide to use the coffee grounds, the climate, and the season. In many cases, using coffee grounds once a month is sufficient. “Using them too frequently can cause nitrogen overload, which could harm plants or grass. The best time to apply them is during the growing season, from early spring to mid-summer, when plants and lawns can take full advantage of the nutrients,” explains Lea.

However, the frequency can change if you’re using compost. Irish-Hanson notes that compost can be applied as needed and usually in the springtime if it’s part of a mulch combination. That said, Langelo recommends avoiding applying coffee grounds on lawns during the warmer months.

About the Experts

• Jonathan Russell-Anelli is a senior lecturer and extension associate within the School of Integrative Plant Science at Cornell University. He has conducted and continues to research how the characteristics of soil change in urban environments influenced by humans. Furthermore, he has contributed to several publications covering soil and factors that impact growth.
• Linda Langelo is a Colorado-based horticulturist with more than 20 years of industry experience. She serves as an extension horticulture specialist at Colorado State University and is the producer of The Relentless Gardener podcast.
• Laura Irish-Hanson is a horticulture extension education at the University of Minnesota. Before her role as an extension educator, she taught classes on plant propagation at the university. She has experience using coffee grounds (making up no more than 10% volume) on plants as part of her vermicomposting under-sink set-up used on in-ground and larger houseplant pots.
• Daniel Barychko has been a horticulturist at the Central Florida Zoo for three years. When not helping to care for the plants at the zoo, he is an active member of the Florida Native Plant Society.
• Luke Gatiboni, Ph.D., is a professor within the Department of Crop and Soil Sciences and an extension specialist in soil fertility and nutrient management at North Carolina State University.
• Andrea Masterson is a horticulturist and collections manager at The Buffalo and Erie County Botanical Gardens. With 10 years of experience, she works to maintain the 12-acre site which houses an arboretum and a multitude of plant collections.
• Stephen Pryce Lea is the deputy executive director of Horticulture at the Delaware Botanic Gardens.
• Wendy Wilber is a Florida master gardener volunteer program coordinator and horticulture extension agent for the University of Florida IFAS. With more than 20 years of industry experience and a master’s degree in horticultural sciences from the University of Florida, she is a specialist in all things landscaping.

Sources

• Steven Fonte, Ph.D., an associate professor in the Department of Soil at Crop Sciences at Colorado State University; email interview, March 18, 2025.
• Washington State University: “myths, miracles…or marketing Coffee grounds— will they perk up plants?” (2009)

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