If you are a coffee addict like me, fertilizing orchids with coffee grounds sounds like a dream come true. It’s organic and available in your kitchen. You can feel good knowing that your used coffee grounds are being put to further use.
However, coffee isn’t always the right answer for orchids. Terrestrial orchids can benefit from coffee grounds as fertilizer. However, epiphytic orchids should never be fertilized with coffee grounds.
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Types Of Orchids
There are two main types of orchids. Terrestrial and epiphytic orchids. They are both members of the orchid family, but they have some big differences in the way they grow.
Terrestrial orchids grow in the soil. In their natural state, they grow on the forest floor, which provides lots of nutrition from decaying plant matter.
Epiphytic orchids, on the other hand, naturally grow on trees. They will attach themselves to the tree with their roots. They are also known as air plants because they have aerial roots. Other popular houseplants that are epiphytic include the pothos and anthurium.
Because they grow very differently, they require different growing mediums and nutrition.
Why You Shouldn’t Use Coffee For Epiphytic Orchids
There are several reasons why you shouldn’t use coffee for epiphytic orchids. Let’s take a look at the facts.
Orchids Love Nitrogen
One reason why orchids are believed to benefit from coffee is that they love nitrogen. Nitrogen is essential for plant growth, but orchids require more than some other plants.
The problem is that epiphytic orchids are not grown in soil. Instead, a special growing medium is used. Soil has bacteria which break down the nitrogen into nitrate. If the nitrogen isn’t broken down into nitrate, it can’t be used by the plant.
Because epiphytic orchids don’t grow in soil, there are no bacteria to break down the nitrogen. Another issue is that epiphytic orchids prefer wet and dry periods. These dry periods would kill any nitrifying bacteria if they did manage to grow in the medium.
These factors make coffee useless in terms of increasing your orchid’s nitrogen intake, at least for epiphytic orchids.
Coffee As Mulch
Perhaps you’ve heard that you should just sprinkle coffee grounds on top of your orchid’s growing medium as mulch. This is also problematic.
First, orchids are typically flushed every few weeks to avoid root burn from fertilizer build-up. This will likely wash away any coffee grounds.
Lastly, coffee grounds can attract gnats and grow mold as it decomposes.
Clogging Substrate
Epiphytic orchids require their substrate to have plenty of airflow. Coffee grounds can make their way into the substrate, and clog it.
Epiphytic orchids have aerial roots. They are designed to be constantly exposed to the air. So, clogging the substrate is highly problematic.
Unfortunately, if coffee grounds clog the medium, it can quickly lead to root rot and stunted growth.
Decomposing Substrate
Orchids are known to be acid-loving plants. Coffee is highly acidic, so it seems like a match made in heaven, right? Unfortunately, no.
Orchids prefer soil that is slightly acidic. Coffee is highly acidic, which is far from ideal for Epiphytic orchids.
Coffee’s acidity can also speed up the decay of the growing medium. As the medium decays, it becomes compact. This causes it to hold too much moisture, and limits the airflow to the orchid’s roots.
What About Tannins?
Coffee has a high amount of tannins. It’s believed that these tannins can stimulate root growth in orchids. However, there are no studies to back up this claim.
The truth is, we don’t know if tannins are beneficial to orchids. What we do know is that tannins increase the acidity level, which speeds decomposition of the growing medium.
Benefits for Terrestrial Orchids
Even though coffee shouldn’t be used on epiphytic orchids, it can be beneficial for terrestrial orchids.
Better Soil Quality
Coffee grounds can actually improve the soil quality for terrestrial orchids. It improves water retention and soil aeration. It also improves soil drainage.
Plant Nutrients
Coffee contains nutrients that are highly beneficial to orchids. These include nitrogen, potassium, phosphorus, copper, and magnesium. There are other beneficial nutrients as well, but these are the ones that are available in sufficient quantities to provide real benefits for your orchids.
Because terrestrial orchids are grown in soil, the nitrogen is broken down into nitrate over time, which makes it available for use by the plant.
How to Use Coffee Grounds for Terrestrial Orchids
There are two basic methods for using coffee grounds as a fertilizer. These are “coffee tea” and compost-containing coffee grounds.
Coffee Tea
To make coffee tea, you’ll need 2 cups of used coffee grounds and a 5-gallon bucket of water. Place the coffee in the bucket. Add enough water to cover the coffee grounds completely.
Let the mixture sit for 24 hours. Then, filter out the coffee grounds, and place the coffee tea in the fridge.
You can then use the one-part coffee tea with 3 parts water to fertilize your orchids. Do this once or twice a month during the growth phase.
Coffee Compost
The compost should contain 5-20% coffee. Other ideal ingredients are wood chips, newspaper, or dry leaves, which are all high in carbon.
Once the compost is ready, you can add it to the soil of your terrestrial plants.
Fertilizer For Epiphytic Orchids
Coffee isn’t the best choice for epiphytic orchids. However, there are other organic fertilizer options that will provide them with what they need.
The best organic fertilizer for orchids is surprising at first glance. It’s fermented citrus juice.
What You Need for Citrus Fertilizer
To make citrus fertilizer, you’ll need citrus peel, sugar, and water. Pretty simple, right? Don’t worry if you don’t have a huge amount of fruit peels on hand. You can add more as you get them.
Any citrus peel is fine. You can use lemon, orange, grapefruit, or pineapple.
You’ll also need a plastic jug. It’s easier if it has a wide mouth because you’ll be tossing citrus peels into it. If the mouth is small, just cut the peels to fit.
Making Citrus Juice Fertilizer
You’ll add 3 parts fruit peel, 1 part sugar, and 10 parts water. The easiest way to do this is to measure the height of the jug. Then divide it into 14 equal parts. You can use a marker to mark each section for easy measuring.
Start with the sugar, filling the bottle to the first line. Then add the water. It should come up the 11th line.
Then, add your fruit peels. It’s best to cut or chop it into small pieces because they will have more surface area and ferment faster.
If you don’t feel the jug to the top, continue adding citrus peels when you have them on hand. Allow the mixture to ferment for 3 months. Be sure not to screw the lid on tightly.
As it ferments, it can cause the bottle to build too much pressure and explode. Leaving the lid loose allows the air to escape.
Why Citrus Juice Fertilizer?
You’ve probably heard of lots of fertilizers for orchids. Coffee, eggshells, even banana peels. What makes this superior to those options?
The fermentation process is key here. It allows the orchids to immediately access the nutrients contained within the juice. Plants are not people, and can’t digest foods to extract the nutrients the same way we do.
The juice contains nitrate, potassium, and iron in significant amounts. It also has potassium and phosphorous. Fermentation produces lactic and succinic acids, which are well known to boost plant growth as well.
There’s another benefit as well. Citrus juice smells like orange juice, rather than smelling like rotting organic matter. If you are growing orchids indoors, this can be an important perk.
Lastly, the citrus smell is a natural pest repellant. Keep pests like gnats and snails away while enjoying the citrus scent yourself.
How to Use
Simply dilute one part juice with 20 parts of water, and water your orchids. You can use this throughout the growing season to keep your orchids healthy.
Final Thoughts on Fertilizing Orchids with Coffee Grounds
Terrestrial orchids can be fertilized with coffee grounds, although the citrus juice fertilizer is also a great option for them.
When it comes to epiphytic orchids, coffee can do more harm than good. There’s little benefit to giving this type of orchid coffee. Given that it causes the growing medium to break down and can clog the soil, it should be avoided.
Particularly since citrus juice fertilizer creates a superior fertilizer without the risk. It does require some prep time, but it’s easy to make other than the waiting.
If you need the fertilizer sooner, you can begin using the fertilizer after 1 month of creating it. It won’t be quite as effective at that stage, but it’s still great for your orchids.
Just pour out a bit of the mixture to use, and allow the rest to continue fermenting.
