Skip to main content

When you should (and shouldn’t) put used coffee grounds in your garden

Coffee grounds do have a place in your garden

Person using rake in garden soil.
Image used with permission by copyright holder

Depending on how into gardening you are, you may be aware that putting used coffee grounds in your garden is a highly debated topic. Some people swear by using coffee grounds for growing plants, while others say it’s the worst thing you can do for your garden.

So which opinion is correct, and how do you know which side to trust? How do you know if you should — or shouldn’t — put used coffee grounds in your garden? We’ve researched the pros and cons and broken them down below so you can decide if you want to use coffee grounds in the garden.

Should you use coffee grounds as mulch?

Using mulch in your garden can be beneficial, but many people find the cost of mulch too expensive to turn into organic matter. Straw and compost can be used as mulch, but not many people have tons of straw lying around, and compost takes months to create. So it seems as though coffee grounds would be the perfect solution for gardeners in need of mulch.

However, coffee grounds can actually harm the roots of seedlings by inhibiting growth if applied too thick. Also, coffee contains caffeine, which could suppress the growth of plants. Coffee grounds are tiny particles that are prone to locking together and forming clumps. These clumps can become a barrier to water and other nutrients that the plants need to absorb.

So what is the answer regarding using coffee grounds as mulch? The key is to add them in slowly. Using too much at once can create a barrier for water to get to the soil, causing plants and grass to die. But used correctly, they can aerate the area and provide much-needed nutrients. They can also keep pests away (more on that later) and keep neighborhood cats out of your garden because they don’t like the smell (and likely won’t pee and kill anything around it). Plus, it gives you a chance to recycle your old grounds instead of throwing them away, which is a win-win.

Potted flowers and gardening spade.

Can coffee grounds be used as a fertilizer?

Coffee grounds contain several essential nutrients, such as nitrogen, potassium, and phosphorus, along with several micronutrients — all of which make using coffee grounds for plant fertilizer a great idea. The amount of nutrients in each batch of coffee grounds varies, but ultimately, coffee grounds can be used as a slow-release fertilizer. (Coffee grounds aren’t as acidic as some claim, so you don’t have to worry about that.)

Sprinkle coffee grounds in a thin layer onto your soil to use as a fertilizer. Just make sure you don’t use too much or pile it too closely; just like you have to be careful when using coffee grounds as mulch, you don’t want the particles to clump and create a water-resistant barrier.

Another plus? Worms like coffee grounds and worms are a necessary part of the ecosystem that is any garden. By adding coffee grounds, you’ll be making your green space a little more inviting to worms.

Compost pile
Getty Images

Should I add coffee grounds to my compost?

Composting can be very beneficial. There are two types of compost material: green and brown. Coffee grounds fall into the green category since they are a green material, which means they are rich in nitrogen. (Coffee grounds typically have about 1.45% nitrogen.) Other green materials are food scraps and grass clippings. All of these green materials contain magnesium, calcium, potassium, and other trace minerals.

You can throw your coffee grounds (paper filter and all) into your green compost bin, but when it comes time to put the compost in the garden, you must mix your green compost with some brown compost. Too much green material and your compost will smell, but not enough will defeat the purpose, too: The compost won’t heat up the way it needs to. Brown compost material consists of items such as newspapers and dried leaves. The general rule is to have a 4-to-1 brown-to-green compost material ratio.

Person holding coffee filter with coffee grounds.

Do coffee grounds work as a pesticide?

Many people also swear that used coffee grounds in garden beds will eliminate the slugs and snails damaging their plants. Though the reason is not apparent — whether it is the texture of the coffee grounds or caffeine content, the slimy creatures tend to avoid the stuff at all costs. The same has been thought for ants, but there isn’t any science to back this up. The only way to find out if your garden will benefit from coffee grounds as a natural pesticide is to try it and see if it acts as a barrier to pesky insects. However, you should prepare a backup plan to exterminate the plants’ threats if the coffee grounds don’t work.

Coffee grounds can be a great addition to any garden if you follow the guidelines we’ve outlined above. Used coffee grounds could be the answer if you’re an avid gardener and feel like something has been missing. Whether you need mulch, fertilizer, compost, or pesticide, used coffee grounds could be the mystery ingredient you didn’t even know you needed to take your garden to the next level. And now that you know the facts, you can participate in that heated debate about coffee grounds at the next garden club meeting.

Editors' Recommendations

Kelly Kaliszewski
Kelly's work has appeared in blogs and on websites. When she's not writing, she is playing with her two dogs, cooking, or…
5 things you should always buy at Costco (and 4 you really shouldn’t)
Person grocery shopping with a Costco membership

We all love shopping at Costco. From the food court to the extra benefits — like the tire center, vision center, and pharmacy — there are plenty of hidden perks of shopping at Costco. But this doesn’t mean you should buy everything there. Here are five things you should definitely put on your Costco shopping list — and four you really shouldn’t.

What you should buy at Costco
Rotisserie chicken
Do we even have to say this one? It’s a ready-to-go meal for the whole family. It costs $5. This isn’t something we should have to talk you into. (You should, however, check out Costco’s other prepared foods and pre-made meals. They’re tasty too, and you can find some good deals.)
Maple syrup
Is there anything better than fluffy, warm pancakes with real maple syrup? Too many syrup options out there today are made with the artificial stuff — highly processed corn syrup or high fructose corn syrup. And when you do manage to find the real deal, it’s pretty expensive. Kirkland’s brand is made with real maple syrup, the kind that comes from the sap of maple trees — and it’s got that signature Costco price. And, according to Epicurious, it holds its own in the flavor department.
Gift cards
Gift cards theoretically should be the same price everywhere — after all, you’re essentially just buying money to spend at another store, right? But at Costco, you can often get them at discounted prices. So be sure to stock up for those last-minute gifts for friends and family. (Or for yourself. We don’t judge.)
Vodka
There’s been a persistent rumor for years that Kirkland-branded vodka is actually produced by Grey Goose. And while those claims have been denied, it kind of doesn’t matter: If you can get a bottle that tastes like it could be high-end vodka to alcohol enthusiasts and taste testers all over, then that’s definitely a brand worth spending $20 on.
Over-the-counter medications
If you and members of your household have to take acetaminophen, ibuprofen, or allergy pills regularly, buying in bulk makes a lot of sense. You’ll likely go through the bottle before it expires, will spend a fraction of the price, and will never be caught without a little relief again. Keep a smaller bottle in your bag (or wherever’s convenient for you) that you refill from the Costco bottle and you’re good to go.

Read more
Brighten up your walkway with landscape lighting: What you need to know
how to install outdoor lighting shutterstock 487132054

The exterior of your home is the first place guests access when they're visiting, so it needs to be safe and easy to traverse. That's why having adequate outdoor lighting is imperative. Additionally, if you're selling your home, a stylish, modern outdoor lighting solution gives prospective buyers a great first impression of the property. With a just few lighting updates, you can give your home an immediate facelift and make it more inviting for guests and prospective buyers alike. Here's how to install outdoor lighting.

Can I install outdoor lighting myself?
Adding a lighting concept to your outdoor space doesn't necessarily require a wealth of DIY skills. It does, however, require some knowledge of and comfort with electrical components. There are three main types of electrical systems for landscape lighting, and the method you choose determines the skill level required for the project.

Read more
7 creative ways you can use coffee grounds around the house
Person holding coffee filter with coffee grounds.

If you don’t think coffee grounds serve a purpose after your coffee’s done brewing, think again. While people typically throw them away, used coffee grounds actually have some practical functions that have nothing to do with coffee. There are several different ways to use coffee grounds around the house, and some may even surprise you!

Why toss your used coffee grounds in the trash when they can be used for gardening, cleaning, deodorizing, beautifying your skin, and even more? If you hate being wasteful and are always looking for how to repurpose what others view as junk, then follow these seven creative ways you can use coffee grounds around the house.

Read more