Are Coffee Grounds Good For Tomato Plants? ☕

Are Coffee Grounds Good For Tomato Plants 1

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Coffee grounds contain valuable nutrients that shouldn’t be going to waste. You can use these in your garden to help your plants thrive. But not all species will respond to this type of kitchen waste. So, should you use coffee grounds on tomato plants? 

It’s recommended to avoid giving coffee grounds to tomato plants. The high nitrogen and acidity levels might lead to stunted growth and can turn the leaves yellow. It could also negatively impact the fruit yield. However, there are a few conditions where coffee grounds can help your tomato plants thrive.  

Tomatoes can be very sensitive to changes in soil acidity. Because of this, you will need to be careful about what you add to the garden. This includes exercising caution with using coffee grounds. Keep reading to learn more about how to use coffee grounds around your tomato plants. 

Pros And Cons of Using Coffee Grounds on Tomato Plants

Deciding whether or not to use coffee grounds can be difficult. There are pros and cons to each approach. 

Benefits Of Using Coffee Grounds

Let’s start by talking about some of the reasons why you might want to consider using coffee grounds in your garden. These include: 

  • Contains nutrients. Coffee grounds have a wide range of micronutrients, including things like iron, zinc, and magnesium. However, the main benefit is the high levels of nitrogen that the grounds contain. Even better, this will be released slowly as microbes break down the grounds, releasing the grounds into the soil. 
  • Right pH range. Coffee grounds have a pH level of between 5.5 to 6.8Opens in a new tab.. This suits tomato plants, which tend to prefer more acidic soils. Ideally, your tomatoes will grow in a pH range of 5 to 6.5Opens in a new tab.
  • Can help to suppress weeds. Coffee grounds can act as a weedkiller, stopping pest plants from taking soil nutrients from your tomatoes. 

Downsides Of Using Coffee Grounds

But before you start spreading coffee grounds around, you ought to be aware of the downsides. These negative impacts can include: 

  • Raises soil acidity. This is the biggest concern. If the soil becomes too acidic, your tomato plant will experience stunted growth and might not bear fruit. 
  • Too much nitrogen can harm tomato plants. As we mentioned, coffee grounds are high in nitrogen. Your tomato plant does need this nutrient to grow effectively. But if the soil concentration gets too high, it can start to cause major problems. The plant will grow, and there will be plenty of leaves. But the size of the fruit will be reduced. 

It should be noted that these concerns aren’t unique to tomato plants. There is a range of other species that will struggle when coffee grounds are added to the soil. This article goes into more depth about some of the plants that don’t like coffee grounds and why this type of mulch isn’t suitable. 

When To Use Coffee Grounds

Most of the time, it’s recommended that you avoid using coffee grounds. But there are some situations where coffee grounds can help your tomato plants thrive.  

Deciding Whether to Use Coffee Grounds

As you can see, most tomato plants won’t need coffee grounds. The best option is to test your soil before you apply the grounds. There are a few things that you should be looking for, these include:

  • NPK levels. This will tell you the amount of nitrogen, phosphorous, and potassium. Most fertilizers recommend NPK levels of 10-8-10Opens in a new tab.. However, you can also use a balanced fertilizer with an NPK of 10-10-10. If your nitrogen levels are too low, you might want to use a small number of coffee grounds to raise them again.  
  • pH levels. This test tells you the acidity in your soil. Remember, tomatoes prefer acidic soils, so if it becomes too alkaline, you can use coffee grounds to raise the pH level. Otherwise, your plants might not be able to extract nutrients from the soil, making your plants appear withered and weak. 

The good news is that these tests are easily available. You should be able to find them in your local hardware store. Plus, they are easy to apply. You just need to follow the instructions on the package. 

In these circumstances, you might want to consider using coffee grounds. However, there are some other methods that you can explore. 

Other Ways To Add Nitrogen To The Soil

If you suspect that low nitrogen levels are a problem, there are a few things you can do; these include: 

  • Fertilizer. This is one of the best options. You should be able to find a fertilizer that is specifically made for tomatoes. It’s best to choose a slow-release option, which will last for a few months. 
  • Adding manure. Animal manure is very high in nitrogen. Because of this, you will need to compost it first. This ensures that you don’t accidentally burn your plants. The good news is that manure will take a long time to break down, so it can provide enough nutrients to last for several months. 
  • Fish emulation. This is known for its high NPK content, often having a ratio of 5:1:1. Because of this; you will need to use it carefully, diluting it in water. 
  • Organic mulch. Grass clippings can help to add nutrients to the soil. As they break down, they will add nutrients back into the ground. 

With all these methods, it’s important to be careful not to overdo it. For example, too much nitrogen can cause as many problems as having too little nitrogen. Because of this, it’s a good idea to take NPK tests regularly to know how you are changing the soil conditions. 

Other Ways to Acidify The Soil

If the soil is too alkaline, your tomato plants will struggle. They won’t be able to absorb the nutrients they need to thrive. However, there are a few ways you can try and lower the pH level to solve this issue. Here are some of the options to explore: 

  • Using ericaceous compost. Ericaceous compost is designed for plants that are intended to be grown in acidic soil. You can mix a little of this into the soil to lower the pH level. It can also be used in the potting soil mix. This article goes into more depth about this type of compost
  • Adding sulfur. This is a good long-term solution and is one of the most effective soil amendments. It’s best to add this during the summer and fall. It’s also best to apply this to the soil before you start planting your tomatoes. 
  • Mixing iron sulfate into the soil. This works similarly to sulfur. However, it won’t be as powerful, so you will need to use more iron sulfate. 
  • Sphagnum moss. This helps your tomatoes in two ways. First, it will help you acidify the soil. The effects will last for a long time. Often, it will last for two years. Secondly, it is organic, adding nutrients to the soil as it breaks down. 

Like with any soil amendment, it’s important to perform regular checks. This tells you how well it is performing, so you can avoid adding too much. The modification may take a few days to change the pH levels. 

Tips To Spot High Soil Acidity

Tomato plants tend to thrive in acidic soil. But if the soil becomes too acidic, it can start to cause some problems. Here are some of the things you should be looking for: 

  • Yellowing leaves. This will also cause the leaves to fall off the tomato plant more rapidly. 
  • Stunted growth. Sometimes, your tomato plant won’t be as large as you expected. At other times, you might find it growing slower or appearing weaker than you expected. 
  • Lack of fruit. This is one of the most common issues. Either you won’t have as much fruit as you wanted, or the fruit will be smaller than you expected.  

If you suspect that high acidity might be the problem, you can perform a pH test to test your hypothesis. Remember, depending on the species, tomatoes need a pH range of 5.5 to 7.0.   Unfortunately, these symptoms will worsen over time, so it’s important to act quickly if you think there is a problem. 

How To Address High Soil Acidity

If the pH test reveals the acidity is too high, you will need to mix some lime into the soil. This helps neutralize the pH. But as tomatoes prefer acidic soil, you need to do regular pH tests to ensure that you aren’t adding too much. 

Signs Of High Nitrogen Levels

There is an easy way to tell if your nitrogen levels are too high. You just need to examine the plant. It will have lush green leaves. But there will be problems with the fruit. Sometimes, the fruit might be undersized. At other times, you might only get a limited number of fruits. It’s also possible that the bloom might be delayed until later in the season when the nitrogen levels in the soil have fallen. 

Even if the fruit does develop, it can still have some problems. For example, it might puff up on the outside while being hollow in the middle. Or it might have a sunken, dark spot at the end of the tomato. If you see these problems, it’s recommended that you get a soil test. 

How To Address High Nitrogen Levels

The good news is that this is an easy problem to address. You just need to sprinkle some colloidal phosphate or bonemeal on the soil. This will counteract the high nitrogen levels in your soil. It’s also best to stop fertilizer for a while, so the soil has a chance to return to normal. 

Applying Coffee Grounds to The Soil

If you still want to apply coffee grounds to the soil, you need to be careful. Doing it incorrectly can cause major problems. 

Most people sprinkle the grounds directly onto the soil. However, this is the wrong technique. The grounds can end up clumping together. This will stop water from getting into the soil. Plus, the acidity and nitrogen levels will be too concentrated, which can negatively affect plant growth. 

Furthermore, there is a chance that plants can be hurt if they ingest the loose grounds. This is due to the high amount of caffeine that is contained in the grounds. 

Here are the steps to take to apply coffee grounds safely: 

  1. Combine a cup of coffee grounds with two and a half gallons of water
  2. Leave the mixture to steep, giving the grounds some time to infuse into the water.
  3. Strain the mixture
  4. Water the garden

This process should help you control the pH levels while retaining beneficial nutrients. The problem, though, is that you can only use a small amount at a time. You don’t have to let your coffee grounds go to waste. You can leave them in an airtight bag while you wait to brew the next batch. 

Another option is to place your coffee grounds into mulch. In this case, you will need to mix the coffee grounds with green waste, like leaves and kitchen waste. Aim for one part coffee grounds to every four parts green waste. Furthermore, you might need to wait six to 12 months for the grounds to break down. 

A third option is to use coffee grounds on a worm farm. This will help you to break it down and release the nutrients. This video goes into more depth on how you can use coffee grounds in your garden. 

Final Thoughts

Coffee grounds can be very powerful. Used correctly, they can inspire huge growth. But if you use them on the wrong type of plant, they can cause a lot of damage. Because of this, it’s important to be careful about how you use the grounds. For example, if you want to apply them to tomatoes, it’s best to steep them in water. As long as you do this, you shouldn’t have any negative consequences. 


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