Is Ground Coffee Good for Plants? Investigating the Benefits and Risks



Home-brewed coffee has long been a staple in many households for a morning jolt or an afternoon pick-me-up. But are coffee grounds good for your plants, too?

Some swear by incorporating these spent grounds into their gardening routine and have successfully fertilised the soil for their plants. Others urge you to stay far away from them because of how they break down in your soil.

Not sure where you fall on the coffee grounds or no coffee grounds debate? We’ve got you covered. This article will teach you what you need to know before using them in your garden this year.

Are Coffee Grounds Good For Your Plants?

Research shows that spent coffee grounds contain many vitamins and minerals that are good for your soil. However, it’s important to note that this method has pros and cons. As we mentioned above, you must be careful before simply dumping them in your flower pot.

Let’s take a look at some of these pros and cons below.

1) They Contain Nitrogen

The idea of using coffee grounds in your garden comes from the fact that they contain about 2% nitrogen. Nitrogen is an essential ingredient in soil composition and is tested in compost regularly.

You’ll often hear the terms “greens” and “browns” thrown around when discussing compost. Greens, like coffee grounds, are things rich in nitrogen, while browns are other items high in carbon. As you build your compost, coffee grounds can be an excellent addition to adding nitrogen to your soil amendment.

In addition to nitrogen, coffee grounds contain potassium, phosphorus, calcium, iron, magnesium, and chromium. These components make using your spent grounds very beneficial — if you do it right.

If you’re adding coffee grounds to your compost, you’ll want to generally keep a 4-to-1 ratio of greens to browns so that the pile heats up correctly and doesn’t smell. It also takes about three to six months to break down completely, so be patient if you use this method.

Note: Some people say that keeping the grounds moist can help them break down better into the soil; however, this is primarily anecdotal, so feel free to try it and see!

2) They Can Act As Fertilizer

While composting is one way to utilise coffee grounds, you can add them directly to your garden beds as fertiliser. However, there are a few more precautions when using this method, and even some studies reject using coffee grounds in this way.

Here are a few of the considerations:  

1. If you use too many or put them in a pile, they can create a water-resistant barrier. Be sure to rake them out evenly across your soil.

2. Fresh-seeded areas can have slower germination rates if exposed to coffee grounds.

3. Some plants, like tomatoes and rhododendrons, can develop brown tips if exposed to coffee grounds.

4. A study from 2016 showed significant suppression of plant growth when coffee grounds weren’t thoroughly composted.

You’ll want to know which plants you’re utilising coffee grounds around, and you may want to experiment independently.

3) They Can Repel Some Pests

There’s nothing worse than having your garden overtaken by pests of any kind!

The caffeine in your coffee grounds may help repel bugs like snails and slugs, so spreading them around younger plants is especially beneficial. However, don’t lay it on too thick, or it will suppress the growth of your plants, too.

There’s some information out there that also suggests that cats hate the smell of coffee and will leave your plants alone as well. However, if you have pets that love to dig and will get into anything, an abundance of coffee grounds can harm them and make them sick. If you have curious pets, you may want to opt for the compost bin option instead of using grounds all over your garden beds.

As with any pest control method, try it and see if it works for you. If not, have a backup plan ready to go.

4) They Make Worms Happy

Worms are an essential part of our ecosystem; you want them in your garden doing all their hard work. The good news is they also love coffee grounds!

So, as you’re looking to utilise them in your garden, you may be doing more than adding nitrogen; you may also encourage worms to take up residence. That’s a huge win!

What Plants Like Coffee Grounds?

Some plants tolerate coffee grounds around them much more than others.

So you can plan your garden and fertilising method out, here are some plants that may thrive with coffee grounds mixed into the soil:

  • Sedge
  • Marigolds
  • Crinum
  • Forget-Me-Nots
  • Hibiscus
  • Iris
  • Lily Of The Valley
  • Elephant Ear
  • Meadowsweet
  • Calla
  • Bugbane
  • Azaleas
  • Blueberries
  • Radishes

On the other hand, the following plants are not big coffee grounds fans:

  • Tomatoes
  • Succulents
  • Orchids
  • Lavender
  • Rosemary
  • Spider plants
  • Black-eyed Susans
  • Snake plants
  • Yucca

This is where garden planning and plotting can come in handy. If you want to utilise coffee grounds you’ll want to know exactly what you’re planting where and what the soil composition is like. This will help you avoid costly mistakes and prevent brown leaves, low germination rates, and more.

Plan your garden accordingly!

Can You Use Any Type Of Coffee Grounds For Your Plants?

It’s important to note that any coffee you use around your plants should be black — leave that cream and sugar for your cup!

In addition, you’ll want to closely examine which types of coffee you’re looking to use.

Unspent Coffee Grounds

If you’re looking to boost your soil with unspent coffee grounds, you’ll want to ensure you’re regularly testing its pH levels.

While it’s great to want to use any coffee grounds you have at home that may be past their expiration date, grounds that haven’t been brewed carry a higher acidity rate. And, in most cases, you don’t want to overdo it and risk killing your plants or having them not sprout at all.

Leftover Liquid Coffee

If you’re on TikTok, you’ve likely seen people telling you to dump any leftover liquid coffee you have into your pots around the house. This can be a great way to add some nitrogen to the soil; however, as with our previous point, don’t overdo it, or you may make your soil too acidic.

Refer to our list of “coffee-approved” plants above, and then do some of your research before you go too far with this method.

Diluted Liquid Plant Fertiliser

You can dilute coffee grounds like leftover coffee, making a more liquid-based fertiliser. This helps the coffee grounds not carry too much acidity and is often used to get soil mixes just right for planting.

Whole Beans

While they don’t break down quite as quickly or effectively as coffee grounds, you can add whole-bean coffee to your compost.

Give them plenty of time to break down, though, so they can add the right amount of nitrogen to your soil amendment.

Pre-Mixed Specialty Coffee

As mentioned above, you only want to use black coffee in your garden. Pre-mixed cold brew blends can contain high amounts of sugar and other unwanted ingredients.

How To Source Coffee Grounds For Your Plants

So, are coffee grounds good for your plants? There’s a lot to know! But we hope these tips above give you a good place to start.

At Grounds, we believe coffee should be an experience — from start to finish. That’s why we offer a host of coffee blends for you.

Add our ground or whole bean coffee to your morning routine and try to utilize the garden coffee grounds. Just remember that ground coffee can be composted more quickly than whole bean, and decaffeinated coffee may not have the same pest-repellent properties as regular coffee.

However, if you know which plants can tolerate a nitrogen boost and test the soil when necessary, try experimenting with different nitrogen blends.

To source your grounds, you can stop into one of our cafes and grab a bag to take home or order our delicious blends online. However you source it, remember you can do various things with your leftover grounds and coffee.

If you didn’t finish your last cup of coffee and it was black, you may want to pour it into a flower pot or garden with plants that enjoy acidic soil. Have a compost pile started? Throw the filter and grounds into the pile and rotate it regularly to add greens and nitrogen into the mix.

With myriad ways to incorporate it into your routine, we think you’ll enjoy giving your plants the soil amendment they need to grow into beautiful flowers, fruits, and vegetables!

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