A few months back I was talking to my grandma and she told me that her mom would sprinkle coffee grounds in the garden; she would tell me how her garden was the best in the county and her thumb was greener than her plants.  

It was this conversation that inspired me to make K-cup seed starters for my garden. Talking with grandma can be everything you need to get your garden growing.  Of course, this was many moons ago, but coffee and gardening haven’t changed too much. 

Coffee Grounds on Top of Your Plant Soil

After I learned of this used coffee ground magic in the garden, I started doing some research on the subject. Afterall, I’m not the first person to learn about this method. As I dug deep on the internet, I realize my great-grandma was on to something, possibly even more so than she realized. 

While coffee grounds are best for acid loving plants, it should still be used in moderation. Just by sprinkling some of these magic coffee grounds on your soil top, you can help deter pests, but you will want to watch the family dog. Used coffee grounds can be added to compost and worms absolutely love it, although you want to be careful not to overdo it. 

Acid-Loving Plants 

I can just imagine my great grandma in the early 1900’s; making coffee and breakfast, cleaning up the kitchen and heading to the garden with her coffee grounds. She named all her plants because as she would say “when the plant feels the love, it will grow to show it” and I absolutely agree. 

I am not sure if she put coffee grounds on all her plants or if she knew that acid loving plants like azaleas, blueberries, lilies, and hydrangeas would benefit the most. In my research I discovered that while many vegetables like slightly acidic soil, tomatoes don’t do well when coffee grounds are added to their soil. 

Root plants like radishes and carrots like to have the coffee grounds mixed with the soil at planting time, that is when they respond most favorably. 

I have a hydrangea that was given to me almost dead. It was bare, just sticks in the ground. I named her Angel, and this baby has become a big bush of love. It is the prettiest plant I have, she is proud with extra green foliage. If plants could smile, Angel would be grinning. 

Every week I would sprinkle a little bit of coffee grounds on to Angel and give her some water. Within a couple weeks she started producing leaves and, in a few months, she was full of life again.  

It’s important to understand that not all plants are the same, some are going to thrive in acidic conditions while others will wilt. The only thing every plant has in common is that they really love to be loved.  

Pest Control 

I have considered that my great grandma knew fresh coffee grounds would suppress weeds and some fungal pathogens. Sprinkling coffee grounds on top of the soil can help deter some pests, it won’t fully eliminate them, but it will help keep rabbits, cats and slugs away, while minimizing damage to the garden. 

The theory I found said that caffeine in the coffee grounds has negative effects on the pests and so they avoid soil that has been sprinkled with coffee grounds. There are claims that coffee grounds on the soil will also repel cats from using your garden beds as a litter box. 

Large doses of caffeine can be harmful, and it is hard to say what a large enough dose would be since the amount of caffeine in used coffee grounds can vary. I would say that if you have a dog that is happy to sample anything that smells somewhat agreeable, you should avoid laying coffee grounds directly into the garden. The best thing to do would be to add your coffee grounds to your compost heap instead. 

There is a suggestion I found that I would love to try, it said that you can use decaffeinated coffee to avoid potential issues. The coffee I buy is Organic unflavored coffee, I wouldn’t use flavored or non-organic coffee because it can be bad to add things to the garden or the body that we’re unsure about. 

Composted Coffee Grounds 

Coffee can be added directly to soil, but you should understand the benefits of adding it to your compost. When coffee is added to compost, there will be more nitrogen in your compost. Adding coffee to your compost is an awesome way to use something that would typically end up taking up landfill space.  

Coffee grounds are considered green compost material and you will want to balance them out by adding brown compost material to your compost pile. 

There are many benefits to using coffee grounds as a fertilizer; it adds organic material to the soil, improves drainage, water retention and aeration in the soil. Using coffee grounds in compost can help microorganisms that are beneficial to plant growth as well as attract earthworms. 

Fresh coffee grounds are acidic, but if you rinse the used coffee grounds, they will become near neutral at a pH of 6.5 and this should not affect the acid levels of the soil. If you want to use coffee grounds as fertilizer, you can work the grounds into the soil around the plants. Leftover, diluted coffee can work well too. 

For those who do vermicomposting, you can use coffee grounds as worm food in the worm bin. Worms actually love coffee grounds. It is important to note that coffee grounds should be given in moderation to keep the worms home at proper acidity levels.  

Adding egg shells with the coffee grounds can reduce the acidity. Another way to keep the worms safe is to pre-compost the coffee grounds for three weeks and then add it to the vermicomposting bin. Paper coffee filters can also join your coffee into your worm bin. 

Coffee, Coffee, Coffee! 

I love coffee, I’m the mom that has the “But first, coffee” shirt and I have been begging my husband to let us try to grow our own Arabica plant just to have homegrown coffee. Of course, my dreams and my climate are two different things. 

Gardening can be hard, but having a successful yield is rewarding. I always think about my grandma telling me “you can only reap what you sow” and I am happy to sow a lot. 

Talking to my grandma in the morning while I drink my coffee on my porch admiring my pretty plants is the best way to start the day. I don’t know if either of us realize how much we learn until we think of our conversations in retrospect. 

I’m thankful that the green thumb was passed down to me and that I have successfully brought plants back to life with a little coffee grounds and a lot of love. 

I think many other gardeners could benefit from adding coffee to their lives and their gardens. The warm morning drink and the nitrogen boost to the compost. These reasons are enough to keep me sipping and encouraging others to make the most out of what they are already using. 

There are many coffee houses or coffee shops that will give you their used coffee grounds for free, so if you aren’t a coffee drinker there is nothing to worry about, your garden will be happy with your Starbucks used coffee grounds.