How to Use Coffee Grounds in a Garden

By Amanda Lutz Updated February 7, 2024

Coffee drinkers should think twice about tossing their grounds in the garbage: Coffee grounds are made of organic matter that can encourage healthy growth in a garden. However, excess application can have the reverse effect and damage plants. Read our guide below for tips on how to help your garden flourish by adding just the right amount of fresh coffee grounds.

Benefits of Using Coffee Grounds in Your Garden

Coffee grounds contain micronutrients such as calcium, magnesium, boron, copper, iron, and zinc that make it an ideal soil amendment. Plus, caffeine can deter or even exterminate some pests. Read more about the benefits coffee offers your garden:

Common Misconceptions

Coffee grounds can encourage plant growth, but they can be harmful to your garden when applied in large quantities. Read more about common misconceptions and why too much coffee can negatively impact your garden.

Myth: Coffee Grounds Acidify the Soil

Many garden enthusiasts apply coffee grounds to acid-loving plants such as azaleas, hydrangeas, and blueberries because they believe it can lower soil pH levels. However, the acid in coffee beans is water soluble, and most of a coffee pot’s acid ends up in cups of coffee. After brewing, coffee grounds are closer to pH neutral, between 6.5 and 6.8.

Myth: More Is Better

Adding too much coffee to your garden in any form can do more harm than good. Excess coffee in your garden can cause these disappointing results: 

Myth: Coffee Grounds Can Be Used as a Primary Fertilizer

Coffee grounds contain many nutrients, but they don’t release nitrogen right away. Gardeners must add a nitrogen fertilizer such as composted manure, alfalfa meal, or grass clippings to their gardens to provide garden plants with adequate nutrition.

How to Use Coffee Grounds in Your Garden

The safest way to use coffee grounds is by adding them to compost. Coffee grounds contain nutrients such as phosphorus, potassium, magnesium, calcium, and nitrogen, which are ideal for the composting process. Grounds shouldn’t make up more than 20% of the composting mixture. 

You can also make coffee into a liquid fertilizer called a soil drench that you can apply to soil or plants. This mixture can also serve as a pest deterrent.

Applying grounds directly to your garden can improve soil drainage and aeration. Add grounds gradually, and avoid overuse.

Composting Coffee Grounds

You can add coffee grounds and coffee filters to a compost mixture that is four parts leaf clippings to one part coffee grounds. Adding coffee grounds to your compost increases nitrogen to improve soil health and promote plant growth. 

Coffee grounds are considered green matter in composting because they contain nitrogen. If you use too much green compost material, your compost bin will start to smell. If you use too little, compost won’t heat up enough to be effective. Be sure to balance coffee grounds with brown compost material.

Direct Application

Applying coffee grounds directly to soil as a type of fertilizer is a delicate process that requires precision and care. Spread a thin layer on top of the soil, and then work the grounds into the top few inches of soil with a rake. If you spread grounds too thickly over the soil, fine coffee particles can compact and form a barrier that doesn’t allow air or water to penetrate.

To use coffee grounds as mulch, mix them with leaves or bark before applying the mulch to your garden. Turn over the soil surface with a rake to incorporate grounds into the soil.

You can also apply coffee to your garden as a liquid. Mix one part water with two parts strong brewed coffee and then apply the solution to the soil. Or, mix nine parts water and one part coffee, and spray that solution directly onto plant foliage and stems.

Our Recommendation

Coffee grounds are useful supplements to compost mixtures and fertilizers and can help your garden flourish. Mind your measurements, as an excess of coffee can be hazardous to plant growth. Consider enlisting the help of professional lawn care services to keep your garden in good health.

Using Coffee Grounds in a Garden FAQ

Can I just sprinkle coffee grounds in my garden?

Yes, you can sprinkle coffee grounds into your garden. Spread the grounds thinly, and mix them into the soil completely.

Which plants don’t like coffee grounds?

Plants that don’t like coffee grounds include geraniums, Chinese rye, and Italian ryegrass.

When should and shouldn’t I put used coffee grounds in my garden?

You should put used coffee grounds in your garden if you grow plants that thrive in acidic soil or neutral soil. You shouldn’t put used grounds in your garden if you grow plants that prefer alkaline soil.

Do all plants like used coffee grounds?

Not all plants like used coffee grounds. Seedlings and plants that thrive in alkaline soil typically don’t respond well to the use of coffee grounds.

Do coffee grounds keep mosquitoes away?

Coffee grounds can keep mosquitoes away somewhat, but the effect won’t be long-lasting. The smell of strong coffee overpowers odors that mosquitoes are attracted to, so it acts as a temporary repellent.