Coffee grounds are a great way to fertilize your garden. Learn how to use coffee grounds in the garden to improve your soil & help your plants thrive!

Millions of Americans start their day with a cup of coffee – but many don’t realize that the spent coffee grounds are great for the garden, and can be recycled into nutritious soil for plants. Whether you have a few houseplants or a big garden, coffee grounds can give your plants a boost – just like coffee gives you a boost in the morning!

There is a common misconception that coffee grounds are particularly good for acid-loving plants like blueberries or hydrangeas. In fact, while coffee itself is acidic, most evidence shows that the used grounds have most of the acidity removed, and they are actually close to neutral, so they will not significantly affect the pH of your soil (unless you are using fresh grounds, as we will discuss below as well).

However, composted coffee grounds are an excellent source of nitrogen for your plants. They also contain potassium and phosphorous, which help prevent plant diseases and encourage flowering and fruiting.

There are a number of ways that you can use coffee grounds for the garden to improve soil health and plant growth. Here are 10 great uses for coffee grounds in the garden:

1.) Add Them to Your Compost

Whether you have a large compost pile or a small compost bin, you can add coffee grounds directly to your compost to break down over time and create a rich source of fertilizer for your garden. You can also recycle used coffee filters as long as they are the paper kind. (We prefer the unbleached ones, especially for an exposed pile where they may take longer to break down.)

Although they are brown in color, you should be aware that used coffee grounds are considered a “green” material when it comes to composting, and they will need to be balanced out with the addition of some brown materials such as shredded dry leaves.

2.) Fertilize Your Plants Directly with Used Coffee Grounds

If you don’t have a compost pile, you can also fertilize your plants directly with coffee grounds. However, you will want to keep in mind that while coffee grounds do add nitrogen to your compost as they break down, they don’t immediately add nitrogen to your soil if you are using them as a direct fertilizer.

However, they will add organic matter to the soil, which helps to improve soil texture, leading to either improved drainage or moisture retention, depending on the type of soil you have and what it needs. Adding coffee grounds to the soil can also help to support microorganisms that are beneficial to plant growth.

When using coffee grounds in the garden as fertilizer, simply work them gently into the top layer of the soil around your plants.

3.) Make Coffee Ground “Tea”

You can also fertilize your plants with coffee ground “tea.” To make the tea, just add 2 cups of used coffee grounds to a 5-gallon bucket of water. Let steep overnight to ferment slightly and allow the water to absorb the nutrients from the grounds. Use the tea as a liquid fertilizer for garden or container plants. It is also mild enough to use as a foliar feed for most plants, which can be sprayed directly on the leaves. (Always test on a small patch of leaves and wait 24 hours before spraying the whole plant. Note that some plants, such as tomatoes, may not like coffee as a fertilizer.)

4.) Mulch Your Plants with Used Grounds

If you have access to large amounts of used coffee grounds, you may also use them as a mulch around your plants. This will provide the added benefit of reducing weeds and conserving soil moisture, and the grounds will break down over time to add nutrients to the soil and improve soil texture.

However, you should be aware that a thick layer of coffee grounds will often dry and harden into a shell-like layer which may keep water from getting to your plants’ roots. To combat this, use a thin layer of just 1/2″ inch or so of grounds, and cover this layer with another form of organic mulch like straw, grass clippings, or leaves. This will also encourage earthworm activity and help the grounds incorporate into the soil.

5.) Repel Slugs and Snails from Your Plants.

Although this is purely anecdotal, some people have found that slugs and snails will avoid coffee grounds, so this may help to keep these pests away from sensitive plants. Sprinkle some dry used grounds around the perimeter of tender plants like lettuces and other greens to keep these slimy critters at bay.

6.) Keep Cats Out of the Garden

Some people use a heavy sprinkling of coffee grounds to repel cats from garden beds and keep them from using them as litter boxes. If you have a problem with cats digging in your garden, give this a try. It won’t harm them, and will improve your garden soil at the same time!

7.) Feed Your Worms

If you make worm compost or vermicompost, used coffee grounds are a great addition to your worm bins. Worms love them, and will quickly turn them into rich compost. Just make sure you drain the grounds well and don’t add too many at once, which could make your worm bin too wet or too acidic, which the worms don’t like.

Earthworms in the garden also love coffee grounds, so putting used coffee grounds directly in the soil as mentioned above will help attract earthworms to your garden beds, thus breaking down organic matter more quickly and helping to aerate the soil.

8. Reduce Fungal Diseases

While it has not been scientifically proven in a home garden setting, coffee grounds do have some antimicrobial properties, and there are some indications that they may help to suppress fungal diseases including rot and wilt diseases on some plants.

9. Reduce Weed Growth

There is some evidence that coffee can inhibit seed germination and the growth of some plants. For this reason, you should wait to apply coffee grounds to the garden until after your seedlings have germinated and are growing well. It may help to prevent weed seeds from germinating as well, but you don’t want it to impact your crops, so use caution, and for safety, only use well-composted coffee grounds around young seedlings.

10.) Grow Your Own Mushrooms

If you want to try your hand at growing your own mushrooms, used coffee grounds can make a great growing medium, as they contain most of the nutrients that mushrooms need to grow.

Mushrooms aren’t grown in regular garden soil – they need a special growing medium, so you’ll be growing these indoors. You’ll need to collect your grounds in a container, add mushroom spores and sawdust, and moisten your medium. You can find more detailed instructions here.

Can You Use Fresh Coffee Grounds In the Garden?

You may be wondering if you can use fresh, unused grounds in the garden, and the answer is yes, but with a few caveats. The best way to use fresh coffee grounds for the garden is to sprinkle a little bit around acid-loving plants such as azaleas, hydrangeas, and blueberries. Root crops may also benefit from a few fresh grounds at planting time. However, not all crops like them, so use caution and apply sparingly.

The Bottom Line

There are many ways to use coffee grounds while gardening. Whether for building better compost, improving your soil, feeding your worms, or repelling pests, you’ll find that coffee grounds can be a cheap and sustainable way to provide your garden with nutrients and support. Just use in moderation and pay attention to how your plants respond. You’ll soon find what works best for you when using coffee grounds for the garden.