Over the past few years, much has been written adding and mixing used coffee grounds into compost and in the garden. Acid-loving plants, such as those below are good candidates for fertilizing with used coffee grounds:
- Lily of the Valley
- Gardenia bushes
- Hydrangea plants
- Roses like slightly acid soil
Ground coffee works as a soil amendment for these plants. Be advised that before brewing, coffee grounds contain quite a bit more acid as well as caffeine.
Make Good Use Of Your Coffee Grounds
If you make a pot or fresh cup of coffee every day, you are also producing an excellent organic soil additive. Used coffee grounds are a perfect addition to your vermicompost (worm compost) or compost heap or bin. They are readily usable as an amendment to garden soil.
Compost With Coffee Grounds
When added to compost or vermicompost, coffee grounds are “green” matter, even though they are brown.
Coffee grounds are nearly 2% percent nitrogen. They also contain trace minerals, including potassium, magnesium, and calcium.
You don’t have to do anything special to add coffee grounds to your compost. You can empty your coffee maker’s basket (filter and all) right into the bin.
Do be sure to balance out this rich source of green material with some brown material, such as a newspaper or dry leaves.
An excess of green material will prevent your compost heap or bin from heating properly, causing rotting and a foul odor instead. Ideally, it would be best to have four parts brown matter to one part green matter for perfect composting.
If you are composting with worms, coffee grounds act as grit to help the worms digest. Be careful to keep the right balance of coffee grounds to non-green materials in a worm bin. Too much acidity can be irritating to worms.
Mulch With Coffee Grounds
It’s also an excellent idea to sprinkle used coffee grounds over the surface of your garden soil. Of course, to do this, you’ll want to remove the filters. It’s helpful to let the grounds dry out before spreading them.
When you are ready, rake the soil’s surface and then sprinkle the grounds over the area you wish to treat. Make it a very light layer. If you spread the used coffee grounds too thickly, they will repel water.
Follow up by lightly raking the grounds into the surface of the soil. The right amount of coffee grounds worked into the soil will help with water retention properties and may discourage weed growth.
Amending the surface of your soil with coffee grounds adds nitrogen to the earth. Used grounds are not especially acidic, so you don’t need to worry about adding excessive amounts of nitrogen.
Native earthworms will appreciate the addition of coffee grounds to the soil.
Make Liquid Fertilizer
It is also possible to make a liquid fertilizer using coffee grounds. To do this, you don’t need to dry the grounds. Place a couple of cups of used coffee grounds into a five-gallon bucket and fill the bucket with water.
Let the mixture steep for 24 hours, allowing the coffee grounds and their chemicals to disperse into the water.
You can use this coffee distillation once a month to water your plants, or you can use it as a foliar spray.
Discourage Unwanted Critters
Although worms like the grittiness of coffee grounds, many pest critters do not. You can pour a thick line of coffee grounds around plants to discourage gastropods, such as slugs and snails. They do not like to ambulate across this gritty line.
Neighborhood cats will avoid digging in your garden if you till coffee grounds into the topsoil. Whether it is the smell of coffee grounds or the feel of them that repels them is uncertain, but whatever it is, cats don’t like it.