Using coffee grounds for plants is a bit of a controversial topic. Some people swear by it, while others warn of the dangers of doing it improperly.
Coffee grounds are good for your indoor plants if you use them the right way. Here’s everything you need to know.
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Why are Coffee Grounds Good for Plants?
Coffee grounds contain many nutrients that plants love. One of the most beneficial is nitrogen.
Plants use nitrogen for many things. It’s important for building plant proteins, and it helps in the development of cell membranes and chlorophyll. Nitrogen is essential for photosynthesis, and one of the most important building blocks of a healthy plant.
Coffee grounds are about 1.5 percent nitrogen and a great way to add it to the soil for your indoor plants. They also contain other essential nutrients, too, like potassium, magnesium, and calcium. When you add coffee grounds to indoor plants, they act as a slow-release fertilizer.
In addition to delivering a slow and steady amount of nutrients, coffee grounds help indoor plants in other ways, too. They may deter some bugs from getting into your plants, and they are very absorbent and can help with water retention.
Coffee grounds might even work for keeping curious house cats away from indoor plants, and they can help prevent the growth of some harmful fungi and bacteria.
Do All Plants Benefit from Coffee Grounds?
Coffee grounds are acidic, and the plants that love them the most will be those that like acidic soil. Some common houseplants that fit this category include:
- African violet
- Christmas cactus
- Miniature roses
- Snake plant
- Spider plant
That said, houseplants generally prefer neutral or acidic soil, so when used correctly, coffee grounds won’t harm most houseplants.
Note that a big exception to this is succulents. Most succulents prefer soil that is the same as where they originate from. So, some will like acidic soil, while others will like something a little more alkaline. For best results, do your research before adding coffee grounds to succulent pots.
How to Use Coffee Grounds for Indoor Plants
There are a few ways to add coffee grounds to your plants, and some are more effective than others.
Add to the top of the soil
This method is what most people probably think using coffee grounds for indoor plants means, but it’s actually the worst of the four methods, which may contribute to why people think using coffee grounds is a bad idea.
Many people just dump their coffee grounds on top of the soil, but this can lead to a lot of problems for your plant.
First, coffee grounds are very acidic. When dumped on the top of the soil in this way, the acidity can be too much, even for plants that like acidic soil.
If this is your preferred method, you have to take care to do it the right way so as not to harm or stress your plants. Use a thin layer, no more than ½-inch thick. Any thicker than that and the grounds will create a barrier that prevents air from circulating and water from evaporating, which can lead to moisture problems.
A thick layer of coffee grounds can also prevent the nutrients from getting into the soil, defeating the purpose of using them in the first place.
Mix into the soil
Another approach is to mix the coffee grounds directly into the soil. Mix the grounds into the first few layers of soil so that it doesn’t block the surface and gets deeper, closer to the roots.
Remember that coffee grounds retain water, so consider adding perlite to help with drainage if you go this route. This approach is a little better than adding them directly to the top of the soil, but it’s not the best way to go about using coffee grounds for indoor plants.
Use coffee compost
If you already compost, start adding coffee grounds. This method is the best way to get the benefits of coffee grounds without overdoing it. The nutrients add to the richness of the compost that you’re already planning to use for your plants.
If you don’t already compost, what are you waiting for? Most people collect kitchen scraps, like fruit peels, eggs shells, and unused pieces of vegetables, into a metal container. Toss in your coffee grounds, and let the organic materials break down naturally. Then, add it to your plants!
Make a liquid compost
Liquid compost is an excellent way to deliver coffee grounds to your indoor plants while also avoiding any of the pitfalls. It’s a little easier to do than regular composting, though it’s not quite as well-known.
Mix one part coffee grounds to four parts water in a glass jar or large plastic jug. Let it sit for two weeks, mixing it at least once a day. In time, the coffee grounds break down, and all of the beneficial nutrients are now in the water. Then, use your liquid compost to water your plants.
Here are a few things to keep in mind when using coffee grounds for houseplants:
1. Don’t use them on baby plants. If you’re growing seedlings, the high levels of nutrients in coffee grounds are likely too much for them. Wait until the seedlings grow a few adult leaves and you repot them before adding coffee grounds.
2. Water after adding coffee grounds. If you’re using any method that involves dry coffee grounds (as opposed to liquid compost), add or mix the coffee grounds or compost into the soil and then water. Watering after applying ensures everything blends well and the nutrients get delivered.
3. Don’t overdo it. If you’re applying the ground directly to the top of the soil, remember, keep them thin. For small three or four-inch pots, a tablespoon is often enough.
4. Coffee grounds can be very harmful to pets. Keep houseplants with coffee grounds out of reach of your cats and dogs.
When used in moderation, coffee grounds give your house plants a boost of nutrition that can help them thrive. Make sure you don’t use too much and go for composting over direct application if you can.