Coffee grounds composting best practices

Last Updated on: 9th February 2025, 08:49 am

The Composition of Used Coffee Grounds

Coffee grounds contain valuable nutrients like nitrogen, potassium, phosphorus, and various micronutrients that gardeners crave. Rich in organic materials, they help improve soil structure and provide a slow release of nutrients.

Do coffee beans or grounds affect pH Levels?

While the grounds are slightly acidic, their effect on soil pH is usually neutral since they decompose. Adding them to compost won’t significantly alter the pH level of your soil, making them suitable for most plants.

Despite what some may tell you, adding coffee waste on plants directly is not an appropriate soil adicifier. In fact, putting the grounds onto the plants themselves can be toxic.

Here are the reasons to add coffee to your composting efforts:

Used grounds reduce or eliminate the need for commercial nitrogen fertilizer

Coffee grounds are a fantastic source of nitrogen, a crucial component of the green ingredients needed for balanced compost. High nitrogen content speeds up the decomposition process, helping to form compost faster.

Used coffee grounds mean more refined compost

The dense organic matter in coffee grounds helps improve the texture and structure of the finished humus. This results in better soil aeration, water retention, and nutrient availability. The improved soil structure will contribute to quicker seed germination rates and healthier plants.

Worm attraction for better plant growth

Many gardeners swear by coffee for attracting earthworms to their compost. Worms are invaluable for composting as they help break down organic material more efficiently, enriching the soil further. Conversely, coffee grounds can help deter some pests – try it to repel slugs and snails.

Tips to Mix Coffee Grounds into the Compost Pile Correctly

Uncomposted coffee grounds will only hit the trash can. So why not add them to the compost bin? Here are tips for success:

Balancing with Browns

To ensure a healthy and nutritious mix, balance the green coffee grounds with brown materials like leaves and straw. Research from the North Carolina State University Ag Extension suggests that a good ratio for beginners is about 2 parts browns to 1 part greens to maintain proper decomposition.

Proper Incorporation of Grounds in the Garden

Mix coffee grounds thoroughly into the compost pile to avoid clumping, creating an anaerobic environment and creating unpleasant odors.

Monitoring Moisture Levels

Coffee grounds retain a lot of water, so monitoring the overall moisture level of your compost pile is important. Keep it as damp as a wrung-out sponge to facilitate decomposition. It’s ready to use when you achieve a fine to medium texture with few visible bits of the original waste you placed into it.

Check with Your Local Coffee Shops for Used Coffee Grounds

If you’re not a coffee drinker, here’s some anecdotal advice on getting used coffee grounds for your garden. Coffee shops go through countless amounts of fine-ground coffee every day while brewing their specialties for their clients. Some large chains pack up the grounds in brown bags and have a designated pickup site in the store. They share these used cofee grounds with the public for free.

Balance is Key When Composting Brown and Green Material

Too much of a good thing can be bad. Adding excessive coffee grounds in your garden can create a dense, compact layer that hinders air flow and slows down decomposition. Use in moderation for best results.

Be sure to layer those spent grounds with other materials, such as:

Dried leaves
Vegetable scraps
Eggshells
Tea bags
Grass clippings
Wood chips
Dead but disease-free plants (not weeds!)
Twigs and cut-up debris from trees
Unbleached coffee filters

It makes sense to add coffee grounds daily, as long as you also regularly add these other items to the bin.

It’s also worth mentioning that concerns about caffeine impacting plant growth are generally unfounded since caffeine degrades quickly when composted. Not to mention, the brewing process removes much of the caffeine.

Apply a red mulch product in your yard — Click the photo to learn when red mulch is a good option.

Acid-Loving Plants Especially Love Spent Coffee Grounds

Most garden plants benefit from adding coffee grounds in your garden soil. But there are some that absolutly thrive in an acidic garden environment:

Roses
Azaleas
Blueberries
Carrots
Hydrangeas
Camelias
Rhododendrons
Tomatoes
Peppers
Radishes
Ferns
Spinach
Lettuce

Watch your plants thrive after adding used coffee grounds to your compost or when mixed with your mulch.

Making Liquid Fertilizer From 1 Cup of Used Coffee Grounds

If you don’t have a compost bin but love the idea of recycling spent coffee grounds on plants, you can make a lightly acidic liquid fertilizer. Dispense the nutritious benefits while watering the garden.

You need:

One cup of spent coffee grounds
5 cups of water

Put the used coffee into 10 cups of water. Steep the mixture for at least a few hours (24 hours is best). Water around the bases of your trees, roses, vegetables, or flowers. Don’t pour the coffee fertilizer directly above the plant but around the base.

Used Coffee Grounds Are Excellent or Your Soil and Plants

Don’t believe the lies about the caffeine in spent coffee grounds hurting your plants – it’s not true, as long as you don’t overdo it. If you want to add used grounds to your composting efforts, it’s worth the work. Your plants will benefit from the addition. Plus, you’ll spend less of your hard-earned cash on chemical fertilization products.

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Author Profile

Deborah Tayloe

Deborah Tayloe is the CEO and co-founder of Tayloe's Lawn Care Services, LLC. She has a B.S.Ed and holds certificates in soil and water management and herbology from accredited programs.