Can I Use Coffee For My Bonsai?

All gardeners are always looking for ways to supplement the feed given to their plants. In these days of ever-rising prices and shrinking earnings, we are all keen to find ways and means of feeding and protecting our plants while saving money.

One of the ways that we can do this is to use the coffee grounds out of the filter. This may sound unusual, but it’s both a fertilizer and a pest deterrent.

First, let’s look at what is in coffee grounds.


Used Coffee Grounds Are Useful Fertilizer For Your Bonsai Trees

What Is In Coffee Grounds?

Coffee grounds are left after ground coffee is brewed into the refreshing drink millions enjoy each day. Each cup of espresso leaves around 20g of spent grounds behind after brewing resulting in millions of tons of grounds being deposited in landfills each year.

Coffee is a natural product, and as such, the grounds will be subject to variations in where it was grown, how it was roasted, how it was brewed, and what water was used in brewing the coffee.

Coffee grounds are packed with nitrogen, which is released as the grounds decompose.

In addition to the nitrogen content, grounds also contain potassium and phosphorus, which completes the three essential macronutrients for bonsai growth care.

We have a detailed bonsai tree care guide with all the relevant information. Check the guide out here!

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The grounds also contain copper and magnesium, both critical micronutrients.

Coffee As A Fertilizer

There are many different opinions regarding the use of coffee grounds as feed for your precious trees. Let’s look at some of the pros and cons:


  • Fresh coffee grounds tend to be acidic, but once used to make that wake-me-up cuppa in the morning, they have an almost neutral pH.
  • They are excellent for plants that need a slightly acidic growing environment.
  • They do add granularity to the soil and can aid in water distribution and aeration.
  • They are high in nitrogen and will decompose in the soil.
  • Coffee grounds add organic material to the soil, which will improve drainage, aeration, and water retention.
  • As an organic material, coffee grounds will help micro-organisms thrive in the soil, greatly benefitting plant growth.


  • If added in too rich a concentration, they can form clumps and work against the good they can do
  • They are not suitable for trees that are picky about soil pH.

Coffee As A Plant Protector

Slugs and snails will avoid coffee grounds at all costs, as the sharp edges injure their soft bodies. This makes coffee grounds an excellent means of keeping these pests away from your trees, especially those that live outside.

Sprinkle a layer of coffee grounds around the edge of the pot, and slugs and snails will not cross this border.

A thick layer of coffee grounds will also double up as a mulch, reducing weed growth and retaining water.


Coffee In The Compost Heap

As we have said, coffee is high in nitrogen, so it makes an excellent addition to your compost heap.

The entire filter with the spent grounds can be thrown into the heap. The paper filter will decompose rapidly, and the coffee grounds will also deteriorate, adding nitrogen to your mix.

Coffee grounds are considered green compost ingredients, so remember to balance your coffee grounds with brown or carbon-rich ingredients to get that ideal mix.


Whether from your machine or plunger or your local coffee shop, coffee can be a valuable resource for the bonsai tree enthusiast. Our tiny creations may not have room to spoon much coffee into the pots, but it can be a great addition to your compost heap, and all gardeners, irrespective of what they grow, always need a top-notch compost heap.

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Catheryn B


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