The use of coffee grounds as a fertilizer for plants has been a controversial topic.
While a lot of research suggests that coffee is not good for plants, especially herbs, a lot of gardeners use coffee for their plants. Is coffee ground good for mint?
Yes, you can use a moderate amount of coffee grounds for growing mint for enhancing soil quality and providing nutrients like nitrogen, potassium, and phosphorus.
Even with all the debate of whether or not coffee grounds are good for your plants, a lot of gardeners use coffee grounds to fertilize their plants as they are packed with nutrients.
Why coffee grounds are beneficial to Mint?
Coffee grounds roughly contain 2% per volume of nitrogen, which is the most abundant nutrient in it. Mint needs nitrogen for good growth.
Nitrogen is essential for the growth of new leaves and stems, along with being an important component for chlorophyll that helps in the process of photosynthesis and gives the plant its green color.
Potassium is another nutrient present in coffee grounds that are necessary for the mint plant.
It helps in the healthy growth of mint leaves and also tolerates stresses like underwatering, heat, or low light. Potassium makes up 0.6% of one volume of mint.
A very tiny amount of phosphorous, 0.06% is present in coffee grounds, which is also one of the main nutrients that the mint needs for the development of roots and flowers.
Apart from that, coffee grounds also contain micronutrients like copper, magnesium, boron, zinc, calcium, and iron, all necessary for the good growth of the mint plant.
Other Benefits of using coffee grounds for mint
Keeps pests away
For years, coffee grounds have been used by gardeners to keep away pests that try to destroy the plants. Pests like snails and slugs are deterred by coffee grounds.
Coffee grounds also act as a binding agent for a lot of chemical as well as organic pesticides and keep pests away for longer.
Caffeine and other compounds in the coffee grounds keep away bugs as well.
However, some researchers do not agree with this theory and do not think that coffee grounds are effective for keeping pests away.
Keeps pets away
Coffee grounds also keep pets away.
Cats are known to dislike the smell and taste of caffeine, so cats may avoid going near your mint plant or using it as a litter box if you have used coffee grounds on your mint.
Prevents diseases
Diseases are often attracted to plants that have weak immunity or are low in some of the other nutrients. Using coffee grounds can help your plant keep away a number of diseases.
Coffee grounds contain a lot of nutrients that make your mint plant healthier. They also help in keeping away pests that can bring diseases or weaken your plant.
The fungus and mold colonies that build up in the coffee grounds can help prevent the growth of pathogenic bacteria and fungus that cause root rot and other diseases.
Improves the quality of soil
Coffee grounds act as a conditioner for the soil. It improves the structure of the soil as well as the flow of the water.
Coffee grounds are also rich in nutrients. Including them in your soil will improve your plant’s potting mix and compost.
Many studies show that coffee grounds contain 2% nitrogen per volume, but some studies show it to be 10%. Nitrogen helps in the growth of leaves.
Coffee grounds also contain other important nutrients like copper, iron, magnesium, potassium, and phosphorous that aid the soil and the mint plant.
Improves water retention capacity
Coffee grounds are known to improve the capacity of the soil to retain water.
If you use more than 5% coffee grounds per soil volume, it can restrict the airflow and moisture from flowing out.
Improves drainage capacity
Mint cannot grow well in soggy, water-logged soil. Mint has fragile roots, so it needs soil that is loose in texture so that the roots can grow easily.
The organic materials in coffee grounds help improve the drainage capacity of the soil.
Improved drainage will prevent any water-logging in the soil and thus prevent the roots from drowning or root rot.
Increases the acidity of the soil
Ideally, mints require slightly acidic soil, between pH 6.0 to 7.0.
Coffee grounds are acidic and therefore help in increasing the acidity of the soil. However, be sure to check the pH of your soil first, as too much acidity can spoil your plant.
Disadvantages of using coffee grounds on mint
Here lies the controversy, coffee grounds have the potential to be bad for growing mint plants. Let us look at a few of these actors below.
Moisture retention
Coffee grounds contain fine organic particles of clay as well. When you use coffee grounds as mulch, they will bind together to form a barrier for moisture.
It will also prevent air and water from seeping into the soil, leading to soil that is very bad for the mint plant.
Breeding ground for fungus
Coffee contains organic matter that retains moisture.
If you add a lot of coffee grounds to your soil, it is going to pack all the moisture in the soil, creating a soil that is a perfect breeding ground for a lot of fungal growth.
The moisture, acidity, and the high nitrogen content of the coffee grounds will together also invite the development of mildew or mold.
To avoid this, make sure to add other organic materials to your mint as well.
Attract pests
While coffee grounds keep away some pests, they can create ideal conditions for some other pests.
To avoid this, use coffee grounds as compost, rather than applying them directly to your plants.
Stunting mint growth
If your potting mix is sufficient in nitrogen, adding coffee grounds will create an excess of nitrogen, which can inhibit the growth of the mint.
The caffeine in the coffee grounds will be absorbed by the plant along with the water.
Once inside, the caffeine will cause problems in the growth of the mint plant, especially if the plant is younger or still a seedling.
Risky to the soil
The mint requires soil that is slightly acidic. Coffee grounds are very acidic.
So, if you have soil that is sufficiently acidic, adding coffee grounds to it will make it even more so, ruining the plant in the process.
How much and how often should you add coffee grounds to your mint?
Using coffee grounds even a tiny amount more than recommended can harm your mint.
You should be very careful while using coffee grounds. The ratio of the coffee grounds to the soil shouldn’t exceed 5% of the volume of the soil.
Adding more coffee grounds can stunt the growth of your mint plant.
It is preferred that you add coffee grounds to compost rather than directly to the soil. However, if you do add it directly, ensure that you use less than ½ inch of the grounds.
A thick layer of coffee grounds will compact in the soil, making it difficult for the soil to absorb water. it will also prevent air circulation in the soil.
You should add coffee grounds to your soil very occasionally. You can be slightly generous in the early spring right before the mint starts to develop new growth.
But after that, you should only use coffee grounds every 4 to 6 weeks.
How to use coffee grounds on mint?
As compost
The safest way to use coffee grounds on a mint plant is as compost. You need to make sure that the coffee grounds do not make up for more than 20% of the total compost volume.
You can also mix one part coffee grounds with four parts green feedstock or sawdust by actually weighing them.
If you exceed the 20%, your compost might not heat up enough to activate the microbes that work on breaking down the organic matter to release nutrients in the soil.
If you feel that the coffee grounds will make your soil more acidic than needed, you can balance it out by adding lime or wood ash to the compost.
As organic fertilizer
You can also use coffee grounds directly as a fertilizer. However, your plant will benefit only if it is used sparingly, so do not use a lot of it.
The coffee grounds as a fertilizer will release nutrients like nitrogen, magnesium, copper, iron, potassium, and phosphorous. You can add it in the top one or two inches of the soil, or just spread it on top of the soil.
Early spring is the best season to use the coffee grounds as a fertilizer.
Mixed with mulch
You can use coffee grounds mixed with mulch on your mint plant as well. Just spread a thin layer of ½ inch over the soil, not more than that.
Using a thicker mulch of coffee grounds will pack up the soil and create a barrier that will prevent air and water from entering the soil.
Cover the mulch with organic matter like compost or wood chips in a two to four inches thick layer.
Adding to the potting mix
Mint needs soil that is loose and well-drained with some organic matter. For this reason, you can mix the coffee grounds directly into the soil while repotting or transplanting.
Coffee grounds release nutrients slowly. This is good, as your mint plant will get nutrients gradually, instead of being overwhelmed all at once.
Coffee grounds in your potting mix can provide your plant with nutrients for up to six months.
For this reason, you also need to put in a fast-acting liquid fertilizer as well. It will provide nutrients to the plant while the coffee grounds work on releasing the nutrients.
Watering after application
If you are applying coffee grounds directly to the soil, you probably should water your plant right after. The water will help dissolve some of the caffeine that can be harmful to the plant.
It will also help the organic particles in the coffee grounds seep into the potting mix. Also, your plant could be thirsty and might need water.
Do not use coffee grounds on seedlings
The most important thing to remember is never to use coffee grounds on young plants or seedlings. While coffee grounds can be a good fertilizer for adult mint plants, they are not good for young plants.
The acidity and the caffeine present in the coffee grounds are not good, especially for young plants. Caffeine can inhibit the growth of plants. It can affect the growth of seedlings as well.
Not only that, the organic particles in coffee grounds form a cement-like barrier in the soil that prevents water and air from entering the soil.
Yes, Coffee grounds can be good for your mint if used with caution.
