Have you ever dumped coffee grounds in a plant pot at your backyard or front door and wondered if you have committed a crime? Don’t kill yourself with guilt; studies have found that coffee grounds contain essential nutrients that can help your plants grow.
Indeed, coffee is probably one of the most popular drinks in the world. However, what do you and coffee shops do with the remaining coffee ground after brewing your drink?
Some throw this waste away because they cannot produce quality drinks again. If you are a victim of throwing coffee grounds away, read through this piece to see its uses.
Coffee grounds have many uses, from skincare to home uses; however, this article will primarily focus on its use in gardening as a fertilizer.
Can You Use Coffee Grounds as Fertilizer?
Coffee grounds make excellent fertilizer because they contain several vital nutrients necessary for plant growth. The best way to use coffee grounds as fertilizer is to sprinkle them onto your plants’ soil. Coffee grounds are rich in nitrogen and have low potassium, phosphorus, calcium, iron, chromium, and magnesium, making them an excellent fertilizer.
These minerals are essential for plant health, so introducing them into the soil is beneficial. However, since coffee grounds take time to decompose, you may not see an immediate improvement in your plants.
Note that uncomposted coffee grounds are not considered a nitrogen fertilizer. In a study, researchers from the Oregon State University discovered that lettuce seeds showed poor germination rates and stunted growth compared to those planted in a potting mix without uncomposted coffee grounds.
Coffee grounds are a gradual fertilizer, releasing their nutrients slowly into the soil. Furthermore, they are organic fertilizers and are considered eco-friendly. You will significantly minimize harmful chemicals entering the soil when you substitute synthetic fertilizers with coffee grounds.
You will contribute to a more natural and organic landscape, thus balancing the ecosystem and protecting local waterways.
You might be wondering if you can compost bread or rice, check these articles to find out.
Tips For Effectively Using Coffee Grounds as Fertilizer
So, you are probably wondering how to use the coffee ground as fertilizer for your backyard garden. You can do this in two ways: as compost and apply directly to the soil.
1- Use Coffee Grounds In Compost.
You can add coffee grounds to your compost and make an excellent fertilizer. Compost consists of several organic matters like veggies, twigs, leaves, and animal manure, which are good sources of nutrients.
Adding coffee grounds to the compost increases its temperature and speeds up decompositions. Putting coffee grounds into the compost helps you get nutrients for your plant development.
Compost helps your garden by opening the soil structure, thus allowing microbial exchange and aeration. You can also add filter paper to the compost mix to help reduce greenhouse gas emissions.
When the compost is ready, you take them to the farm and spread it as manure for plant nutrients. You can use the compost on the soil before planting or spread it in a garden with grown plants.
Coffee grounds are a great nitrogen source for composting. When composing coffee grounds, add 25% of coffee grounds to the compost pile at sustained temperatures between 140 to 160 degrees Fahrenheit for up to two weeks for better results.
See also: Bokashi And Compost: Which One Should You Pick?
2- Apply Coffee Beans Directly Into The Soil.
You can also apply coffee ground directly to the soil, enabling your plants to take advantage of the available nutrients. However, ensure you use small quantities of coffee grounds. Why?
Coffee grounds are fine; if you use a large quantity, they can compact into hardcover in the soil, thus preventing water or moisture from penetrating to nurture the plant. Therefore, instead of providing nutrients, coffee grounds could prove disastrous for your plants.
You also want to avoid applying coffee grounds into the soil as fertilizer when planting seeds or seedlings because the caffeine may hinder germination or root development.
However, root crops like carrots and radishes respond favorably to coffee ground mixed with soil during planting. Just be sure not to rely wholly on coffee grounds as a fertilizer since it may affect some useful microorganisms.
Mix it with nitrogen fertilizer when adding coffee grounds directly into the soil because coffee grounds stimulate the growth of microorganisms in the soil, which require nitrogen to grow and reproduce.
plantsheaven.com
Will Coffee Grounds Kill Weeds?
Generally, coffee grounds kill weeds. The reason is that coffee grounds are weed suppressants, preventing germination, especially if you use damp ones from the kitchen. The heat generated by coffee grounds can kill pathogens and weeds when sprouting.
The allelopathic properties of coffee grounds stunts germination, thus killing weeds before they see the light of day.
The ideal way to use coffee grounds to control weeds in your garden is to apply them topically since this reduces their negative impact on the plants.
You can use no more than a half an inch thick of coffee grounds on the soil, but ensure you leave spaces near the plants’ roots so that water can penetrate.
Other Ways to Use Coffee Grounds in Gardening
Besides fertilizer and killing weeds, coffee grounds have many other gardening functions. Consider some of them:
1- Mulching
High temperatures make farming challenging because it facilitates evaporation and soil dryness. Mulching will help retain moisture on the ground, allowing your plants to thrive during dry seasons.
Unlike straws and sawdust that may cost you money, coffee grounds are often from coffee shops, and you can easily use them to retain moisture. Coffee grounds are fine and can easily compact to form a layer that retains water in the soil.
However, it is important not to overuse coffee grounds for mulching because caffeine can negatively impact plants’ root development and seed germination.
Additionally, using lost coffee grounds for mulching can lead to a barrier that resists water penetration to the roots, leading to plant death.
Researchers from Washington State University recommend against using pure coffee grounds as a mulch. They suggested instead using a thin layer, less than 0.5 inches (1.27 cm) of coffee grounds and covering with a thicker (4 inches (10 cm)) layer of coarse organic mulch like wood chips.
2- Natural Pesticide
You can spread coffee grounds around plants prone to slug damage. Two theories often explain coffee grounds’ pesticide characteristics: the texture is abrasive, making it unattractive for soft-bodied slugs, or the caffeine could harm the slugs.
Some compounds in coffee, like diterpenes, are also considered toxic to insects; thus, coffee grounds can help repel bugs. Since they deter beetles and fruit flies, they can help keep other pests away.
Coffee grounds help maintain high temperatures in compost piles, which helps reduce potentially dangerous pathogens and kill seeds from weeds and vegetables added to the piles. Also, coffee grounds enhance soil structure and attract earthworms.
About 25 percent of coffee grounds in a compost pile keep the temperatures in the piles between 135 degrees and 155 degrees for more than two weeks, which is enough to kill a good amount of the pathogens and seeds, found researchers from Oregon State University.
3- Prevention of Harmful Fungi
Coffee grounds can help prevent harmful fungi and wilts from invading your plants. Natural fungi colonies are used to decompose coffee grounds and can help fight fungi harmful to your garden.
If you grow crops like peppers and eggplants susceptible to wilts, you could minimize the chances of attack by including coffee grounds during the planting process.
You could pinch a little coffee ground and throw them in the planting hole.
4- Enhances Good Worm Population
Worms are good for the soil by helping in decomposing the compost and readying soil nutrients. Worms on your farm are good news to plant root health.
These organisms love moderate coffee grounds, so you can regularly add them to your compost to enhance the worm population.
5- Soil Drainage
You can also use coffee grounds to amend your soil and improve its quality. Adding a few cups of ground coffee can be an excellent way to improve your garden’s soil drainage.
Coffee ground improves drainage by increasing the organic materials, thus preventing water from settling at the roots of the plants to cause rotting.
If you are a gardener, you know how vital drainage is for your plant health, hence the need to use coffee grounds.
Ensure you properly mix the soil with the coffee grounds to reduce its ability to form a compact that can create a counter-productive barrier.
Which Plants Thrive With Coffee Ground Fertilizer?
It is essential to note that contrary to what most people believe, coffee grounds are not acidic; the acid in coffee is generally water-soluble, so the acid is mainly in the coffee, according to the Oregon State University.
Used coffee grounds have a neutral pH value (between 6.5 to 6.8 pH), meaning acid-loving vegetable plants like carrots, cabbage, radishes, potatoes, squash, soybeans, and turnips will grow well with coffee grounds.
The table below shows a list of plants that grow best in coffee ground fertilizer
| Plants | Genus name | pH requirements |
| Rhododendron | Rhododendron Spp. | Rhododendrons thrive in soils with a pH of 4.5 to 6.0 and do not like soils with high calcium levels. |
| Hydrangea | Hydrangea Spp. | Hydrangeas tolerate a broad range of soil pH, giving different bloom colors. (source: University of Minnesota) – Acidic soils (less than 5.5 pH) will produce blue flowers. – Alkaline soils (higher than 6.5 pH) will produce pink flowers. |
| Cyclamen | Cyclamen persicum | The best soil pH level for Cyclamen plants is about 5.8. |
| Tomato | Solanum Lycopersicum | Tomatoes thrive in USDA zones 2-10 under full sunlight. They prefer loamy and well-drained soil with a pH between 6.0 to 6.8. (source: UIC Heritage Garden) |
| Potato | Solanum Tuberosum | Potato generally requires well-drained sandy loam soils with a pH of 5 to 5.5. (Source: University of Illinois) |
| Broccoli | Brassica Oleacea Var. Italica | Broccoli grows best at a neutral pH level, between 6.6 to 7.5. |
| Peppers | Capsicum Annuum | Pepper plants grow best in soil pH of 6.2-7.2, or even neutral to weakly acidic. |
Are Coffee Grounds Good For Plants And Trees?
Coffee grounds are excellent for plants and trees because they enrich the soil with nitrogen, potassium, and other minerals, which improves soil quality and plant growth. Start by checking your garden’s soil pH using a test kit to determine if the plants or trees will thrive with coffee grounds in the soil. A pH level less than 7 is acidic.
If your soil’s pH is 7 or higher, adding coffee grounds to the soil might not benefit your plants and trees.
However, adding coffee grounds can slow down the growth of certain plants.
For example, seed germination of alfalfa and white and red clovers was impeded by water drained through coffee grounds, found researchers from Washington State University.
The same study also discovered that coffee grounds inhibited the growth of crops, including Chinese mustard, komatsuna, Italian ryegrass, geranium, and asparagus fern.
Are Coffee Grounds Good For Flowers?
Coffee grounds are excellent for flowers, particularly those that thrive in neutral to slightly acidic pH levels. Coffee grounds are a great, slow-release nitrogen source. And nitrogen is a critical component in producing flowers, fruits, and vegetable plants develop.
Additionally, coffee grounds are an excellent organic material added to the soil.
You can use coffee grounds to enrich your soil and provide an excellent base for your flowering plants that contains trace minerals and holds moisture better than some soil types.
Coffee grounds smell amazing, so you will not have to hold your nose while mixing them into the soil.
Check your garden’s soil pH with a test kit to determine if your flowers will benefit from coffee grounds in the soil. A pH of below 7 is acidic. While many flowers thrive in slightly acidic soil. Any flowers that thrive in soil with a pH less than 6.8 will love coffee grounds.
How To Compost Coffee Grounds
- Sprinkle the coffee grounds directly on the soil and mix them into the soil. But, remember, if you allow coffee grounds to dry out, they can block the water in mulch, similar to dry peat moss.
- Add coffee grounds to your compost pile by layering the components using:
- 1/3 of leaves
- 1/3 of fresh grass clippings
- And 1/3 of coffee grounds.
- Scatter the coffee grounds on the soil and cover them with leaves or compost, or bark mulch.
- Mix coffee grounds into the soil and ensure that you keep them moist. Add some nitrogen fertilizer as coffee grounds promote the growth of soil microbes, which use nitrogen. While microbes are breaking down the coffee grounds, the nitrogen fertilizer will provide a source of nutrients for your plants.
- Remember to add coffee grounds as parts of a static compost pile, meaning organic matter is amassed up and broken down by bacteria. Whenever you add coffee grounds to your compost pile, add an equivalent amount of a carbon source like shredded paper or dry leaves. Mix them all together well.
- Remember to turn your compost pile once a week. And it will take about three to six months for the coffee Grounds compost to be ready.
See also: Top 6 Electric Kitchen Composters On The Market (Read this before you buy!)
Final Thoughts
Coffee grounds can act as excellent fertilizers for your plants by providing nutrients such as nitrogen, phosphorus, magnesium, and iron.
However, you should know how to use it; otherwise, it can be counter-productive. Using excess coffee ground can result in a hard, compact layer that prevents water from penetrating the soil causing the plants to dry.
Coffee grounds also have compounds that inhibit germination and root development; therefore, they should not be used when planting seeds or seedlings. The best way to use coffee grounds as fertilizer is by mixing them with compost before using them in your garden.
