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How To Water Indoor Plants With Coffee

Indoor plants add some beautiful greenery to your home, but they need certain nutrients to keep their healthy color. Knowing how to water indoor plants with coffee can help with this.

Coffee contains an excellent source of nitrogen and other nutrients that help your indoor plants thrive. However, there are important aspects to using coffee to water your plants that you should be aware of. This includes knowing how to dilute and when you’ve used too much. 

How Coffee Benefits Your Indoor Plants

Plants need key nutrients to survive as humans do. Coffee can be an excellent source of some of these key nutrients because it contains:

  • Magnesium
  • Nitrogen
  • Potassium

How Magnesium Benefits Plants

A single cup of coffee contains about 7 mg of magnesium. Magnesium is important because it is what gives leaves their green color. 

The chlorophyll in your plant’s leaves needs magnesium to capture the sun’s light. Leaves that are deficient in magnesium cannot photosynthesize and will begin to die. 

The Benefits of Nitrogen

Nitrogen is one of the most important nutrients to plants. It is what helps them grow by synthesizing proteins and chlorophyll along with other key aspects of plants.

Coffee contains about 2% nitrogen, making it an excellent source of this main nutrient. 

The Importance of Potassium

A single cup of black coffee contains about 116 mg of potassium. 

Potassium not only helps plants grow faster but also fight diseases and resist pests. Coffee offers an easy source for plants to obtain this important nutrient. 

Always Use Black Coffee

When using coffee to water your plants, always make sure it is black. Never water your plants with coffee that contains:

  • Cream
  • Flavorings 
  • Sugar

Not only are these additives not beneficial to your plants, but they can also attract bugs. The last thing you want is gnats flying around your house and their larvae attacking your plant’s roots. 

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Therefore, unless you drink your coffee black, it is best to just use leftovers still in the pot, not from your cup. 

Dilute the Coffee

Each type of plant has its preferred pH range. Since coffee is acidic, it can quickly push the pH of your soil far out of that range if you do not dilute it. 

When plants are in too acidic soil, they are not able to absorb nutrients as well. This, therefore, defeats the purpose of adding coffee to increase key nutrient uptake. Hence, why it is so important to dilute your coffee.

Optimal pH for Plants

Coffee has a pH between 5.2 and 6.9 depending upon the preparation and variety. 

Some plants prefer more acidic soils than others, but most plants prefer a pH between 5.8 to 7. As you can see, coffee often falls well below this range which is why it needs to be diluted with water to make it less acidic. 

How To Dilute Your Coffee for Plants

The coffee you water your plants with should be only about ¼ coffee. The other ¾ should be water. 

How much water you have to add may be dependent upon how strong you brew your coffee. If you are someone who likes a very strong brew, you may find that you need to add more water. 

Essentially, your coffee should be mostly water and look like a weak tea before you use it for your plants. 

How Much Should You Water Your Plants

When watering with coffee, you should give your plant the same amount as you would with just water. The amount will of course vary by plant. 

Always give your plant about ¼ of the pot’s volume in water. If the water flows right through and comes out the bottom, then the soil did not absorb it and you will need to water it again. 

You will know if you have given your plant too much coffee water if the soil appears soupy. 

How Often You Should Water Your Plants With Coffee

Since coffee is so acidic, even when watered down, you should not water your plants every day with it.

Instead, limit your watering to about once a week. 

If you are using the coffee to water a plant that is watered infrequently, the time between coffee waterings may be longer. 

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As a general rule of thumb, don’t water your plant every time with coffee even if it’s a plant you only have to water once a week or less. Water it with just water for a few waterings in between each coffee watering. 

How Do You Know If You Have Given A Plant Too Much Coffee?

Plants that have received too much coffee will have stunted root growth and yellow leaves. If it appears your plant is starting to struggle, you should stop watering it with coffee. 

You may be able to add basic materials such as lime to your potted plant to correct the soil pH if it becomes too acidic from the coffee. Be careful not to add so much that your soil becomes too basic, as this can also harm your plant. 

If time passes and the plant does not begin to recover, you may have to remove it from the soil and place it into new, less acidic, soil. 

Use A Soil Tester To Check pH Levels

If you are worried you may be adding too much coffee to your soil, you can easily check the pH. You can either use an at-home test kit or various do-it-yourself methods. 

The test kit will be most beneficial to you though because it can give you a more accurate reading of the soil pH. Do it yourself methods often only tell you if the soil is basic or acidic. Since you want your soil to be slightly acidic but not too acidic, they will probably not be that helpful. 

Plants That Thrive On Acidic Soil

Some plants do better with being watered by coffee than others. This is because they thrive in more acidic conditions. A few of these plants include:

  • Abutilons
  • African Violets
  • Aloe
  • Amaryllis 
  • Azaleas
  • Begonias
  • Ferns
  • Gardenias

Even though these plants love acidic soil, you still should not water them with coffee every time. They too can experience harmful consequences from soil that is too acidic. 

Plants That Don’t Do Well With Acidic Soil

All plants will benefit from the added nutrients that coffee gives them. However, some plants should have their coffee intake more carefully monitored than others. 

This is because some indoor plants do better with soil that is more neutral or slightly basic. 

A few of these plants include:

  • Bee balm
    • A pH of 6.0-7.5
  • Canna
    • A pH of 6.0-8.0
  • Crocus
    • A pH of 6.0-8.0
  • Hibiscus
    • A pH of 6.0-8.0
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As you can see, these plants can thrive in more neutral and basic conditions. Adding too much coffee to their soil will quickly deteriorate their health. 

If you own one of these plants, coffee will still add important nutrients, but consider giving them it less frequently than you would an acidic-loving plant such as an aloe

Can You Use Coffee Grounds With Coffee Watering?

Coffee grounds are also nitrogen-rich, making them great for plant growth. However, unlike brewed coffee, they are not acidic. Instead, they have a neutral pH.

You can place coffee grounds in your indoor plant’s soil after watering them with coffee.  

Since your coffee grounds are not acidic, you don’t have to worry about making your soil too acidic by using them with the brewed coffee. However, it is possible to make your soil too nitrogen-rich.

Plants that have too much nitrogen will look healthy and green. However, they won’t be able to flower. If you are noticing that your plant is not flowering as it used to, you may want to limit your coffee ground use. 

Why Are Coffee Grounds Not Acidic But Coffee Is?

Coffee grounds have a pH between 6.5-6.8, making them only slightly acidic but mostly neutral. Nowhere near as acidic as coffee. 

Acid appears mostly in the coffee rather than the grounds due to the acid in coffee grounds being water-soluble This is why it is important to add the grounds after you water to prevent any acid from being released by the added liquid. 

Benefits of Coffee Grounds With Brewed Coffee

Coffee grounds add even more nitrogen to your soil. Combined with the brewed coffee, they add excellent nutrients to your plants. However, they also benefit your plants by:

  • Preventing slugs
  • Deterring cats
  • Deterring rabbits

If you have pets in your home that enjoy nibbling on your indoor plants, coffee grounds may be the solution for you. 

Watering Indoor Plants With Coffee Is Easy

There is no point in letting your coffee go to waste when it can be a great source of nutrients for your indoor plants. Always be sure to water down your black coffee before pouring it into the soil to prevent undesirable pH levels though. 

Your indoor plants rely on you to provide them with the necessary nutrients to grow. Sharing your coffee with them can help to brighten their leaves and strengthen their stems.