Are Coffee Grounds Good for Plants?

By: | Updated: April 13, 2021

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Throwing away used coffee grounds would be a waste of natural resources right? Thankfully there are some ways making use of used coffee grounds and we take a look at these today.

You probably heard it before; are coffee grounds good for plants? Well, let’s take a look.

Are Coffee Grounds Good for Plants?

Many gardeners are divided amongst themselves. Some say it is good because of the high level of acidity and some say it is not – mainly because of the caffeine left in used coffee grounds.

Yes, there is less caffeine in used coffee grounds than fresh coffee ground but a small & un-harmful amount remains.

So you have to figure out when to use them and when not. Generally there are 4 ways to use (used) coffee grounds in the garden:

  • As a fertiliser
  • For composting
  • As a mulch
  • As a natural pesticide
are coffee grounds good for plants

Used coffee grounds as a fertiliser

Most gardeners use used coffee grounds as a fertiliser, placing them right on top of the soil. We are not talking about fresh coffee grounds (unwashed/unused).

Fresh coffee grounds are high in caffeine and are highly acidic, adding a lot of Nitrogen and should therefore only be used for acid loving plants like Azaleas, Rhododendrons or Begonias for example.   

Used coffee grounds on the other hand are near neutral and have a normal PH of 6.5. Which means used coffee grounds can be used as a fertiliser on 95% of all plants.

Used coffee grounds are beneficial in many ways. Such as improving plant growth derived from microorganisms.

If you want to be 100% certain that you do not harm your plants you may opt for low-acid coffee grounds to make your daily coffee.

Used coffee grounds for composting

Throwing used coffee grounds on your compost is a great way of accelerating or jumpstarting your compost.

The nitrogen and other minerals left in used coffee grounds attract earthworms that increase the speed of composting. You can even throw the paper filter (if 100% paper) on top of your compost.

Used coffee grounds as a mulch

Using used coffee grounds as a mulch is a great idea as long as you don’t use too much and ideally add or mix other organic matter such as compost, leaves or soil into it.

Not too much simply because of the left caffeine in used coffee grounds that when used in large amounts can be counter productive. 

Used coffee grounds as a pesticide

Using used coffee grounds against slugs, snails or ants has been proven to be beneficial.

However studies also showed that it won’t work as a fire proof repellent per se. But it was found that certain animals tend to avoid the area where used coffee grounds are spread. 

Which plants like used coffee grounds?

Last but not least we want to take a look at which plants like used coffee grounds as a fertiliser.

Generally the list is big but we do want to mention a few of the most popular plants that like used coffee grounds: 

  • Azaleas
  • Gardenias
  • Ferns
  • Hydrangeas 
  • Japanese Iris 
  • Rhododendrons
  • and much more… 

Conclusion

Generally speaking used coffee grounds are beneficial to plants in many ways. 

The key is to not use too much when used as a fertiliser, mix with other organic matter as a mulch and be careful when using it as a natural pesticide (for plants that do not like acidic matter).

It is safe to say that used coffee grounds (including the used coffee-paper filter) can be thrown onto the compost to accelerate the process. 

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by Brett