As a lifelong coffee enthusiast, I often find myself with a surplus of used coffee grounds. In the spirit of sustainability, I decided to explore various ways to repurpose these grounds. This journey led me to gardening, where coffee grounds are commonly used as a soil enhancer.

A lot of people ask,“What plants don’t like coffee grounds?”

This is a great question, as not all plants appreciate the acidic gift that coffee grounds bring to their soil. So, what plants don’t like coffee grounds? Let’s find out!

Understanding Coffee Grounds

What are Coffee Grounds?

Coffee grounds are the leftover remnants after brewing coffee. They’re rich in nutrients like nitrogen, which makes them a great organic fertilizer for many plants.

The Nutritional Composition

Coffee grounds contain about 2% nitrogen, as well as other nutrients like potassium, phosphorus, and a host of micronutrients. These elements contribute to the rich, dark color of the grounds, and they can benefit many types of plants.

How Plants Use Coffee Grounds

As I’ve mentioned earlier, coffee grounds are full of nutrients like nitrogen, calcium, potassium, iron, phosphorus, magnesium, and chromium, all of which can benefit plant growth.

But how do plants utilize these coffee grounds exactly?

Let’s dive in.

Nitrogen-Rich Fertilizer

Firstly, coffee grounds are an excellent source of nitrogen, which is a crucial nutrient for plant growth. Nitrogen is an essential component of amino acids and proteins, and it’s necessary for the process of photosynthesis. It encourages the healthy growth of leaves and stems, giving plants a vibrant green color. When you add coffee grounds to your soil, the nitrogen they contain is slowly released, feeding your plants over time.

Improving Soil Structure

Furthermore, coffee grounds help improve soil structure. They increase the soil’s ability to hold onto water and nutrients, a characteristic known as water-holding capacity. This is particularly beneficial for sandy soils, which tend to lose water and nutrients quickly. By enhancing the soil structure, coffee grounds can help ensure that water and nutrients are available for plants to take up when they need it.

Boosting Microbial Activity

Last but not least, coffee grounds can boost microbial activity in the soil. The organic material in coffee grounds serves as food for beneficial soil microorganisms. As these microorganisms break down the coffee grounds, they help release the nutrients contained within them, making the nutrients more accessible for plant uptake. This increased microbial activity can also help improve soil health and structure over time.

Why Some Plants Dislike Coffee Grounds

You might be thinking, “Coffee grounds are packed with nutrients and can improve the soil structure, so what’s not to love?” Well, let’s look at it from the plants’ perspective.

Excessive Acidity and pH Levels

Firstly, one of the main reasons some plants do not appreciate coffee grounds is because of their acidity. While many plants thrive in slightly acidic soil, others prefer a more neutral or alkaline pH. Coffee grounds are naturally acidic, and adding too many to your garden can lower the soil’s pH, making it difficult for certain plants to absorb the nutrients they need. Plants like asparagus, rhubarb, and lavender, for example, prefer soil with a more neutral pH.

Nitrogen Overload/ Over Fertilization 

Secondly, while nitrogen is a crucial nutrient for plant growth, too much of it can be harmful. Excessive nitrogen can lead to a lush, green plant, but one that is all leaves and no fruit or flowers. This is because too much nitrogen can inhibit the production of blossoms, which are needed for fruiting. Plants that are more focused on fruiting or flowering might struggle with too much nitrogen in the soil, such as tomatoes or roses.

Potential Allelopathic Effects

Lastly, coffee grounds may have allelopathic properties. Allelopathy is a biological phenomenon where an organism produces one or more bio-chemicals that influence the growth, survival, and reproduction of other organisms. Some studies suggest that coffee grounds can suppress the growth of certain plants. However, more research is needed in this area to fully understand these potential allelopathic effects.

Specific Plants That Don’t Like Coffee Grounds

The List of Plants

Just like people, plants have their own likes and dislikes. Some plants thrive on acidic soil, while others prefer more alkaline or neutral conditions.

Here, we’re going to discuss some of the most common plants that don’t appreciate a caffeine boost from coffee grounds:

Asparagus: Asparagus is one plant that prefers its soil to be more on the neutral side. Coffee grounds might make the soil too acidic for this plant to thrive.

Rhubarb: This tart, vegetable-like fruit is another that prefers a more neutral soil. Rhubarb can struggle to absorb nutrients in overly acidic soil.

Lavender: Loved for its beautiful purple flowers and soothing scent, lavender prefers a neutral to slightly alkaline soil. Coffee grounds may turn the soil too acidic for lavender plants to flourish.

Roses: Similarly, roses might not appreciate the nitrogen boost from coffee grounds. Roses are bloom-focused plants, and an overabundance of nitrogen might hinder their flower production.

Blueberries: While blueberries love acidic soil, the addition of coffee grounds might make it too acidic. This could disrupt nutrient absorption and impact growth and fruit production.

Beans: Beans, such as green beans and snap beans, are sensitive to high levels of nitrogen. Excessive nitrogen from coffee grounds can lead to vigorous foliage growth but poor pod development.

Geraniums: Geraniums prefer a more balanced pH and can be sensitive to the acidity of coffee grounds. It’s best to avoid using coffee grounds around geraniums to prevent potential nutrient imbalances.

Ferns: Ferns generally prefer a soil pH that is slightly acidic to neutral. Coffee grounds, being acidic, can alter the pH beyond the ideal range for ferns, hindering their growth and vitality.

African Violets: These delicate, flowering plants thrive in a slightly acidic to neutral soil pH. Coffee grounds, especially in excess, can make the soil too acidic for African violets to flourish.

Begonias: Begonias are popular for their beautiful flowers and lush foliage. While they appreciate a slightly acidic pH, excessive coffee grounds can create an overly acidic environment, affecting their growth and blooming potential.

Cacti and Succulents: Most cacti and succulents prefer well-draining soil with a slightly acidic to neutral pH. Coffee grounds can disrupt the soil’s pH balance and drainage, potentially causing issues for these plants.

Orchids: Orchids have specific soil requirements, and coffee grounds might not provide the ideal growing conditions for them. They typically thrive in well-draining, aerated media specially formulated for orchids.

Fruit Trees: Some fruit trees, like apple and pear trees, prefer a more neutral pH and may not respond well to excessive coffee grounds. It’s important to research the specific needs of fruit trees before applying coffee grounds as a fertilizer.

Tips to Use Coffee Grounds Safely in Gardening

1) Composting Coffee Grounds

One way to safely use coffee grounds is to compost them first. This will help to balance the nutrients and make them more plant-friendly.

2) Creating a Balance

Another tip is to mix coffee grounds with other organic material. This can help to balance out the increased acidity and high nitrogen content.

3) Dilute coffee grounds with water:

Before directly applying coffee grounds to your garden, consider diluting them with water. This helps prevent concentrated acidity from directly affecting the plants. Diluted coffee ground “tea” can be used as a liquid fertilizer by pouring it around the base of your plants.

Alternative Uses for Coffee Grounds

In the Kitchen

If your plants aren’t fans of coffee grounds, you can use them in the kitchen. They make a great deodorizer and can even be used to scour pots and pans.

Around the House

Coffee grounds can also be used around the house. They can help to remove odors, clean surfaces, and even deter pests.

Conclusion

While coffee grounds can be a great soil enhancer for some plants, others may not appreciate their acidic nature or high nitrogen content. Before you add any to your garden, it’s essential to understand your plants’ needs. However, even if your plants don’t like coffee grounds, there are plenty of other ways to repurpose them! For a list of plants that do like coffee grounds, click here. 

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