Using Coffee Grounds In The Garden: Are They Even Good?

Homeowners usually use coffee grounds to remove odours and scrub the body. But did you know that your garden can also benefit from coffee grounds?

This DIY plant supplement is one of the staple gardening hacks and among the most heatedly debated. For years, gardeners have tested and assessed using coffee grounds as a soil amendment, in compost, and as a natural pesticide.

However, you can not simply add it to the soil; we’ll explain it here in this article so you can decide how to use coffee grounds in your garden to benefit your plants.

Are Used Coffee Grounds Good for Plants?

Yes, and No! Coffee beans contain many essential nutrients and other trace minerals for plant growth – nitrogen, phosphorus, potassium, calcium, and magnesium. Nitrogen contributes to photosynthesis, which drives plant development and grain yield; potassium and phosphorus are responsible for plant maintenance.

But some of the hype on the internet is exaggerated, and adding coffee grounds in the garden must be executed carefully.

The caffeine that lingers in used grounds is a concern. Caffeine is a chemical stimulant that hinders other plants’ growth, resulting in stunted plants and sometimes intoxicating plants, leading to their death.

Benefits Of Coffee Grounds In The Garden

Improves Soil Drainage

Used coffee grounds are a free organic material, so if you need to correct your soil to help enrich soil quality, adding a few cups of grounds every so often can be an excellent practice. Increasing the organic materials prevents water from sticking around at the plants’ roots, which causes rotting.

Ensure you mix the soil well with the coffee grounds to taper its capability to produce a compact that can induce a water-resistant barrier.

Improves Aeration

Compacted soil is a concern for plants since soil particles are pressed together, reducing pore space between them, which means the roots of the plant cannot obtain what they need. Supplementing the soil with any organic material will help crumble the soil and create small holes through which oxygen, nutrients, and water can reach the roots.

Improves Soil Water Retention

Some plants love moisture and love to be in soil that constantly keeps them moist. Any soil will gain from large applications of organic matter as it’ll dramatically improve its ability to retain moisture. Each 1 percent increase in organic matter helps soil hold 20,000 gallons more water. And this will significantly help plants that like to grow in wet soil, as the ground will stay moist for longer.

Encourage Earthworms Population

Worms are valuable for gardens. They roam the soil by tunnelling, creating natural ducts through which water and oxygen can stream. Coffee grounds are perfect, nutrient-rich food for worms. A good garden worm population is good news for plant root health and helps decompose the compost and prepare soil nutrients.
A crate filled with coffee grounds and dirt.

Ways To Use Coffee Grounds In The Garden

Gardeners have started to use coffee grounds in gardening pretty lately. Used coffee grounds are a little acidic and almost neutral in pH, so you don’t have to worry about using them. We have gathered some of the best ways to use ground coffee to benefit your plants.

Using Coffee Grounds As A Soil Conditioner

Coffee grounds break down into a soil-enriching substance to vitalize and nurture good soil structure. Variable particle sizes are key to good soil structure.

Begin by applying a small percentage of coffee grounds as an extra soil amendment or soil conditioner for your plants. Mix a low quantity with your potting soil when repotting a plant. Or sprinkle a few grounds on the soil’s surface and then cover them with mulch. It should be tilled into the soil to a depth of 6 to 8 inches to improve the availability of essential nutrients.

Using Coffee Grounds As A Fertilizer

We all know that nitrogen drives faster plant growth, toughens the stem, and enables chlorophyll production. And thanks to their 2% nitrogen by volume and additional minerals, the grounds are beneficial as a plant’s slow-release fertilizer. If you continue adding these small amounts of nutrients, eventually, your plants will receive just enough.

Mix the coffee grounds with dry materials and work it into the top few inches of your soil with a rake or hoe, or sprinkle coffee grounds onto the soil surface and leave it alone.

You can also make a coffee ground tea. Mix 2 cups of used coffee grounds with a 5-gallon bucket of water overnight. To use the tea as liquid fertilizer, pour it at the base of plants, or use it to water container garden plants. It also makes an excellent foliar feed by spraying the mixture into leaves and stems directly.

Remember, if you use coffee grounds as fertilizer, it is vital to observe correct watering practices. The soil must dry out sufficiently to prevent the formation of mould.

Composting With Coffee Grounds

Compost is the most beneficial organic fertilizer for plants. It is ideal for vegetable or orchard gardens and flourishing indoor plants. Ground coffee accelerates the composting process. They help heat up the compost pile, creating a perfect environment for the good bacteria to propagate. The grounds must comprise barely 20% of the volume of your pile so that they do not negatively impact the balance of good bacteria.

How To Make Compost With Used Coffee Grounds

Building a fruitful compost pile relies on balancing “green” and “brown” materials. Greens materials are rich in nitrogen or protein exploited by microorganisms in the soil for their growth and reproduction. Browns are carbohydrate or carbon-rich materials used to feed microorganisms and provide energy.

Most food scraps, manure, and grass clippings are considered green compost materials. Coffee grounds are a green material. In contrast, brown compost materials are dried leaves, twigs, and newspapers.

  • Compost bin or pile – Add coffee grounds and your paper coffee filters to your compost bin or pile. Add about four times as much brown compost material to your bin as green compost material. If your pile is not heating up, you must add more green compost material. If it’s beginning to smell, you have too much green material. When compost is finished — it must be crumbly and smells like earth —use it as a soil amendment or apply it around established plants as fertilizer.
  • Vermicomposting or worm bin – Worms love coffee grounds; however, never add more than one cup of grounds to your worm bin every week because the acidity could harm your worms. Once the worms have successfully gained access to your food wastes and newspaper, use your vermicompost as a natural fertilizer.
  • Nonprofit organization/Municipal Composting – Most compost facilities will accept all food scraps, including coffee grounds. Remember to observe the organization’s guidance on what materials are permitted in the compost.

Using Coffee Grounds To Deter Certain Animals

Coffee grounds can be used as an excellent protector against pests. Slugs, snails, and ants are not fond of coffee grounds. Create a barrier of coffee around your plants or garden beds, and its rough texture will keep the annoying pests away. It is also believed that the taste and smell of coffee grounds prevent these creatures.

It also kills mosquito larvae, hornworms, and milkweed bugs. Caffeine as an insect repellent or killer disrupts their food consumption and reproduction and leads to bizarre behaviour by repressing enzymes in the insects’ nervous systems.

But be cautioned that some researchers argue with this guideline. You may want to have a ready backup plan if it doesn’t work.

Some gardeners also say that throwing coffee grounds in the garden is one method to prevent the neighbourhood cats from using your garden as a litter box.

Fresh Coffee Grounds For Acid-Loving Plants

Although used coffee grounds are slightly acidic, fresh (unbrewed) coffee grounds are highly acidic. Your acid-loving plants may benefit from fresh grounds, including blueberries, azaleas, camelia, and hydrangeas.

On the other hand, root crops, like radishes and carrots, react productively— mainly when incorporated with the soil during the planting period.

Fresh coffee grounds are considered to suppress weed growth, containing some allelopathic properties, which negatively affect tomato plants. At the same time, some fungal pathogens may also be stopped. But one must be cautious regarding its uses.

Fresh coffee grounds still retain most of their caffeine content and acid.

Some expert gardeners recommend keeping coffee grounds away from freshly seeded areas or very young plants, as caffeine can reduce germination. Used coffee has some allopathic properties that impede the growth of tomatoes.

You can rinse your coffee grounds before using them to make them less acidic. Or mix them with a more alkaline soil amendment like wood ash to stabilize the pH before using.

When Not To Use Spent Coffee Grounds In Your Garden

Sometimes, coffee grounds can be more damaging than beneficial in the garden.

  1. As mulch. Although a thin layer of spent coffee grounds may seem a reliable option for mulch, the grounds’ structure forms a wall as the particles clump and prevent the plant’s development and ripening. Your mulch must breathe to allow water and air in and out of the soil. The key is to mix coffee grounds with other organic matter like leaf mold, sawdust, straw or compost before utilizing it as mulch. You can also rake coffee grounds into the top layer of soil so they can’t stick together and form a rigid barrier that moisture can’t penetrate.
  2. Around dogs. Even if adding coffee grounds as mulch won’t hurt insects, it can harm your pets. Ingesting an enormous dose of coffee grounds can be toxic for dogs. It’s difficult to say what would be an immense enough amount to induce poisoning as the amount of caffeine in coffee grounds varies. If you need to use it in your garden, add the coffee grounds deeper into the ground or incorporate coffee grounds into your compost pile instead of using them directly.
A pile of coffee grounds sitting on top of a parking lot.

Should You Add Coffee Grounds To Your Garden?

Gardening and coffee grounds suit each other. Whether you are composting with coffee grounds or using used coffee grounds collected from a local coffee house, you must know how to use them; otherwise, it can be inefficient. They are a practical addition to your compost heap and soil if exploited with caution and good judgement.

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