Gardeners are known for using any food scraps and leftovers to make compost or even apply them directly to the soil.
One of those famous leftovers that have gained legendary status as adequate fertilizer is coffee grounds, but when you have orchids, you need to think twice before using coffee grounds as fertilizer.
Do orchids like coffee grounds? Coffee grounds are rich in nitrogen, one of the three macronutrients that most plants need to grow and thrive, but coffee grounds can be too acidic for orchids. Since the nutrients in coffee need certain bacteria to release them, orchids might not benefit much if the soil lacks these bacteria.
With that in mind, you should not rely on coffee grounds alone as the sole fertilizer for orchids and other flowering plants.
In the following, you’ll find out more about coffee grounds as a natural fertilizer, why they aren’t ideal for orchids, and which fertilizers will keep your orchids happy and healthy.
Coffee Grounds for Orchids: What To Know
Coffee grounds often go to waste in the trash bin after you finish drinking your brew.
Since coffee beans are organic and have a high content of nitrogen, gardeners often use them to fertilize plants and even add them to their compost pile. If it has nitrogen, then plants will love it, right?
Why Coffee Grounds Are Often Recommended for Plants
The main component that makes coffee grounds such a popular natural fertilizer is nitrogen.
After roasting, the coffee beans contain carbon that, in the presence of certain bacteria in the soil, can be turned into nitrogen and released into the soil.
Coffee grounds also contain smaller amounts of phosphorus and potassium. That trio of nitrogen, phosphorus, and potassium (NPK) are the main macronutrients that plants need to grow, flower, and bear fruits.
Add to that trace amounts of micronutrients, and you have a wholesome fertilizer from something that you’d normally throw out.
When added to compost, coffee grounds break down into organic materials that improve the water retention of the soil and feed the microorganisms in the soil that release nutrients and fight off pathogens that cause plant diseases.
Coffee Grounds Need Bacteria To Release Nitrogen
The only caveat to the coffee-grounds-as-a-good-fertilizer story is that the soil must have certain bacteria to release the nitrogen in the coffee grounds.
Without these bacteria, the coffee grounds are just dust to the plants and have no more benefits than maybe repelling pests and killing some microbes in the soil, but the plants won’t get any nutrients from them.
The same is true for epiphytic orchids that don’t grow in the soil. With no soil, there are no bacteria to break down the coffee grounds.
Orchid Medium Lacks the Necessary Bacteria
Since the bacteria that feed on the carbon in the coffee grounds and release the nitrogen into the soil are not present in orchid medium, relying on coffee grounds alone to fertilize your orchids will result in plants that do not grow well and most likely won’t flower.
If you’re using an orchid medium in the pots, then you should avoid using coffee grounds.
Coffee Grounds May Be Too Acidic, Or Not Acidic Enough
Another issue with coffee grounds and orchids is that, by nature, coffee grounds are acidic. When added to the soil or potting mix, they increase the acidity of the soil.
That said, you’ll need to add a huge amount of coffee grounds to the soil to increase the acidity in a way that makes orchids or other plants feel the difference.
It’s always best to do a soil test to see if the soil’s pH needs adjustment.
Coffee Grounds Can Compact Growing Medium
Coffee grounds are a fine powder. When you mix them with the growing medium, especially if that growing medium has a lot of silt in it, you risk making the medium too heavy.
That leads to compacted soil that hinders the roots of the orchids from growing and developing fully. Compacted soil also retains water for far too long, which causes root rot and other fungal infections.
Using Coffee Grounds as Mulch for Orchids
Since coffee grounds don’t benefit epiphytic orchids or those planted in a growing medium, some gardeners like to use coffee grounds as mulch.
However, that’s a very bad idea for some of the reasons listed above. For one thing, coffee grounds will compact the soil or any other potting mix you use and clog it in a way that leads to poor draining.
Wet soil or a growing medium that’s always wet is bad news for the sensitive roots of orchids.
Root rot sets in quickly, and before you know it, the plants are withering and dying. So, don’t use coffee grounds to mulch orchids.
Best Fertilizer for Orchids
If coffee grounds are off the list of the best fertilizers for orchids, then what can you use to feed your delightful orchids? Here are three of the top fertilizers to use.
Developed by Michigan State University, this authentic fertilizer is designed specifically for orchids.
The fertilizer is mild, so it doesn’t cause root burn, and it is urea free, so it won’t impact the pH levels of the soil or growing medium.
This is another fertilizer for orchids that improves root development and gives you rich and brightly colored blooms. It should be applied once every two weeks during the bloom season.
Better-Gro is rich in phosphorus and doesn’t contain urea. That makes it ideal for orchids since phosphorus is the right nutrient for flowering plants.
Apply the fertilizer once every 4th watering of the orchids. The fertilizer is concentrated, so you should mix 1 teaspoon of the liquid into 1 gallon of water to feed your orchids.
Homemade Fertilizer for Orchids
Here are a few homemade fertilizer recipes for orchids:
1. Nettle Tea
- Pull a whole nettle plant by the roots. Use gloves since the leaves of the plant sting when they come in contact with the skin.
- Place the plant in its entirety in a jar full of water, and mash it with a spoon to break the surface of the leaves and stem and release the nutrients.
- Cover the jar with the lid, and keep it in a ventilated place away from direct sun exposure for 2 weeks.
- Strain the liquid, and dilute it with 10 parts water to achieve a weak tea color before using it to feed orchids.
2. Banana Water
- After eating four to five organic bananas back to back, don’t throw away the peels. Chop it into small pieces, and add it to 4 liters of water in a container. Organic bananas are pesticide-free, so the fertilizer won’t be contaminated with harsh chemicals.
- Cover the container, and keep it away from the sun or any source of heat for 3 days or until the bits of banana peel partially break down in the water.
- Strain the banana water, and dilute it with clean water to reach a weak tea color.
Note: You may want to test this on another plant you don’t mind losing first. I’ve heard some people say this had minimal positive impact and attracted gnats and flies. I talk more about banana water fertilizer here.
3. Rice Water
- Wash 1 cup of rice in 3 cups of water, and strain the rice. You only need the cloudy water.
- Smash eggshells, or put them in a blender to turn the eggshells into fine powder.
- Add a quarter teaspoon of eggshell powder to every 1 liter of rice water.
- You can also soak the eggshells whole in the rice water overnight and strain them in the morning.
- Apply the rice water directly to the orchids. This fertilizer is rich in nutrients and calcium.
How Much Water Does an Orchid Need Per Week?
Orchids need watering twice a week in hot weather in the spring and summer. When the weather cools down, water your orchids once a week throughout the winter.
Orchids growing in small pots (4 inches or less) should be watered once every 5 days all year round. Those growing in 6-inch pots need to be watered once the top inch of the soil dries out.
Do Orchids Like Acidic Soil?
Orchids, like many plants in your garden, prefer slightly acidic soil. Aim for pH levels between 5.5 and 6.5 to keep orchids happy.
Although coffee grounds are rich in nitrogen, they’re not ideal for orchids planted in a growing medium that lacks certain bacteria.
These bacteria are needed to break down the carbon in the coffee grounds and release nitrogen. Epiphytic orchids don’t grow in soil, so they won’t benefit from coffee grounds either.