Are Coffee Grounds Good For Houseplants? What To Know Before Ditching The Grounds

coffee beans with plants

When you walk into your favorite global coffee shop, you might see the sign that offers free coffee grounds for your garden. You wonder if you should grab them before someone else does as you want to help the environment and do good things for your houseplants. But, do you really know are coffee grounds good for houseplants?

The answer is somewhat complicated as coffee grounds, a waste product, can help some plants, but not all. And, finding success with coffee grounds depends on how they are used within the soil and around the plants. So, are coffee grounds good for houseplants? Sometimes, but not always. 

The Acidic Value of Coffee Grounds

coffee beans in a sack

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If you want your plants to benefit from coffee grounds, you should know what plants actually like them. Since coffee grounds are acidic, you should only use them with plants that benefit from acidic soil. 

If you want to put coffee grounds directly on the soil surrounding your houseplants, you should know that your plants might not like it. Because coffee grounds are a waste product, they can have varying pH levels. So, to best benefit from the potential acidity in them, you should move the grounds deeply into the pot, at least six inches, if not deeper. 

You should always be sure the grounds are cool before you mix them into the soil. Even a thin layer of hot coffee grounds can damage nutrients, bacteria, and microbes in the soil. You should only put a sprinkling of grounds because a thicker layer could prevent air and water from getting to the roots of the plant. Cover the coffee grounds with mulch to encourage decomposition. 

Add Coffee Grounds to Compost

three containers of compost

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You can help all of your plants by putting coffee grounds into compost. When you add them to your compost, you allow them to add nitrogen to compost. To get the best out of them, let them cool, then add them to green material and dried leaves. 

Give the grounds three months to compost before you add the material to your houseplant soil. You can then use the dirt on any houseplant without worrying about adding too much acid or caffeine to them. 

How Does Caffeine Affect Houseplants?

​Coffee grounds contain caffeine which can actually be detrimental to plants. Caffeine reportedly prevents other plants from getting what they need to thrive so that coffee beans can get the most nutrients, sunlight, and water. Experts recommend not putting coffee grounds on seedlings because they may not grow. 

Despite the warnings about caffeine and plants, some people actually water their plants with coffee, but only occasionally. They don’t usually use it to water houseplants; instead, they water acidic outdoor plants like shrubs, berry plants, and rhododendrons. If you do water your houseplants with coffee, watch the leaves as they could turn brown from too much acidity. 

If you do decide to put actual coffee in your houseplants, be sure the coffee is black. The cream and sugar you put in your coffee are not for plants. It is also wise to dilute your coffee on a one-to-one ratio. So, if you have one cup of coffee, you should add one cup of water to it before you pour it in your houseplant’s soil. 

Coffee Grounds Could Dry Out Soil

Coffee grounds have particles that are resistant to water. They stick together to keep water from penetrating them, much like clay soil. Because of this behavior, coffee grounds can cause the soil to become dry, primarily when used as mulch. Fortunately, it is possible to use coffee grounds and avoid having dried out soil. 

Instead of using coffee grounds as mulch and spreading it over your soil, mix it with compost or pieces of leaves. Then, rake the mixture in your soil. Doing this prevents the coffee grounds from clumping so that water can move through the dirt to the roots. 

​Avoiding Fungus in Houseplants

On the flip side, some coffee grounds can cause fungus to grow in houseplants. If the grounds you use are moist, they can boost fungus growth, and this can be the death of your houseplants. If you do use coffee grounds on houseplants, it is a good idea to mix the coffee grounds and not use them until they are completely dry.  

If you do put coffee grounds in your houseplants, you shouldn’t use more than a tablespoon or two at any time. To reduce the odds of your plants reacting negatively, you should only use coffee grounds occasionally. Pay attention to what happens to your plants after you add them. Then, play around with mixing grounds with grass or leaves to alter the pH level of the grounds. 

It is also essential to only use coffee grounds that have dried. Even though they will get wet when you water the plants, the coffee grounds will spread through the soil better if they are dry when you add them. Be sure to mix them into the soil rather than leave them sitting atop it. 

​Plants That Like Acidic Soil

When you ask are coffee grounds good for houseplants, the answer is dependant on the plant. Some plants love coffee grounds and some that do not respond well to them. It is best to only add coffee to plants that thrive in acid-rich soil. Not all do. And, not all plants appreciate the acid in coffee grounds. 

The plants that seem to benefit from coffee grounds in the soil are azaleas, roses, gardenias, hydrangeas, and rhododendrons. Blueberries, but not all berry plants, also like coffee grounds. Most of these are not used as houseplants. But, African Violets, that are often found inside of homes do not benefit from coffee grounds. 

​Other Food Waste That Houseplants Like

Some other foods have waste that plants like. They include: 

  • ​Bananas
  • ​Eggs
  • ​Nuts
  • Oranges

The peels and shells from these foods can be beneficial to some plants, but not all, just like coffee grounds. 

​How to Use Banana Peels

Banana peels can help your plants in several ways. Aphids do not like banana peels. Dust doesn’t like banana peels, either. Peels fertilize the soil, too. Plants like the potassium, phosphorus, and calcium found in the skins. Since banana peels rot, you have to be careful that they do not create mold in your soil. 

The best way to add banana peels to houseplants is by creating a banana peel tea. Adding peels to water and letting it steep in the refrigerator makes healthy plant water. You can make a slurry from the banana peels after steeping them and add that to the soil, too. Some people cut up the peels and put them into the dirt to keep aphids away. 

Along with watching for rot and mold, watch for fruit flies, too. Bananas are attractive to them. You can use bananas to keep insects away from your plants. 

Use a plastic container (like a margarine tub) and poke holes in the lid. Put the banana peel and some apple cider vinegar in the tub and watch the bugs make their way into it. But they won’t get out! You can use this contraption in your house and your garden. 

​How to Use Eggshells

Chicken eggshells have calcium, iron, phosphorus, and magnesium; all are good for houseplants. Unfortunately, eggshells do not decompose quickly, so if you want to add shells to your houseplants, you should grind them finely. 

Another option for eggshells is to steep them, like tea leaves. After 24 hours of steeping, pour the nutrient-rich water into the pots. You can also use eggshells as mulch, just be sure that the eggshells are clean, so mold doesn’t grow. But, since banana peels rot, you cannot add them directly to the soil. 

​How to Use Nutshells

Instead of leaving nutshells behind at the ballpark, bring them home and use them in your houseplant pots. Put peanut shells and pistachio shells in the bottom of your houseplants to help with drainage. Be sure to rinse the salt from them first, so they do not dry out your houseplants.

Nutshells help the soil maintain moisture so that you can use them as mulch on the top of your soil, too.  

​How to Use Orange Peels

Experts recommend keeping orange peels and other citrus peels out of compost piles. So, to keep them out of the trash, use them on your houseplants. Dogs and cats are not fans of citrus, but pets do like to get into houseplants. When you put citrus peels on the top of your soil, your pets will keep their noses and paws out of your houseplants. 

Fresh peels work better than dry ones, so you can refresh the citrus as you enjoy your morning oranges or grapefruits or another tasty citrus.