Vermicast, or pure worm castings, is often used interchangeably with vermicompost. However, vermicast has a higher nutrient density, making it a rich fertilizer for your plants.
You can use pure vermicast for your plants if you use it in conjunction with other soils. You should not plant a plant in vermicast alone. Vermicast provides many minerals and nutrients that support the healthy growth of plants, but they still need other planting media to grow.
In this article, I will discuss the benefits and disadvantages of vermicast, as well as which plants benefit from it the most. I will also explore your options when using vermicast for your plants.
Benefits of Vermicast for Plants
Vermicast contains many minerals crucial for your plants’ healthy growth. Here are some of the nutrients in vermicompost and how they can benefit your plants:
- Phosphorus is essential for the development of strong roots and the prevention of disease.
- Magnesium allows plants to absorb phosphorus and create chlorophyll.
- Nitrogen is essential for protein and amino acid production.
- Potassium is essential for plants that need to survive in hot climates.
- Calcium assists in the development of a strong structure and helps the plant balance its internal pH levels.
- Boron allows plants to utilize calcium. It also is essential for the reproduction and pollination of plants.
- Zinc also plays a vital role in plant reproduction. It helps with growth and water retention in plants, which is crucial for plants in hot temperatures.
- Iron works with magnesium to allow plants to produce chlorophyll to maintain a healthy green color.
- Copper helps to absorb iron and produce amino acids and proteins.
- Sulfur allows plants to absorb most of the other minerals listed above. It also plays a role in photosynthesis, assisting the plant in turning light into energy.
So, when you add vermicast to your plant’s growing media, you can expect to see:
- Healthier Plants: Vermicast helps keep plants healthier by killing bacteria that threaten plant health.
- Larger Harvest: Food plants fertilized with vermicompost yield more produce than their counterparts.
- More Flowers: In a study conducted on hibiscus plants in vermicompost, the American Society for Horticultural Science found that using vermicompost allows plants to produce 93% more flowers.
- Brighter Colors: Vermicast also makes flowers much more vibrant than plants without it.
- Faster Plant Growth: Vermicast boosts plants’ growth hormones, which speeds up germination. This faster growth rate often leads to an earlier harvest.
- Great Seed-Starter: Some gardeners prefer to germinate seeds before planting them outside to allow them time to begin growing without having to push through dense soil.
- Better Water Absorption: Due to the aeration of worm castings, they can hold a great deal of water. That means you do not have to water your plants as frequently, which is particularly helpful in high temperatures where water evaporates quickly.
Disadvantages of Vermicast for Plants
While vermicast has many beneficial nutrients, you must be careful not to cause nutrient toxicity.
Nutrient toxicity happens when you give a plant too many nutrients. When it is overloaded, it will not be able to absorb all of the nutrients it needs and will absorb too much of others. Since each nutrient performs a different function, the plant will not be able to live if it lacks several minerals.
Signs of nutrient toxicity include the death of leaves, stunted growth, and root damage. However, it may be too late to save the plant once you notice these signs.
What Types of Plants Do Not Benefit From Vermicast?
Although vermicast has many advantages, not all plants benefit from it.
Desert plants do not benefit from vermicast since it may be too nutritious and moisture-retentive. Desert plants grow well in sandy, dry soil that has few nutrients, so vermicast may introduce symptoms of overwatering or nutrient toxicity in succulents, cacti, and other desert plants.
Vermicast is full of nutrients from which most plants benefit greatly. However, the nutrient requirements of desert plants are much lower than other plants because they are not used to nutrient exposure in their native sandy soil. This adaptation makes them much more vulnerable to nutrient toxicity.
While most plants benefit from vermicast’s ability to hold plenty of water, this can be detrimental to desert plants. These plants prefer sandy soils that do not hold water well and have adapted to this environment by retaining lots of water in their leaves.
Due to this characteristic, the roots of desert plants do not need much water. On the contrary, too much water can lead to root rot and the subsequent death of the plant.
When vermicast holds water around the roots, it creates the perfect condition for root rot to set in. Therefore, if you use vermicast on desert plants, it should be used as a thin top layer of worm tea that will not come into contact with the roots.
For a more in-depth look at the effect of worm castings on desert plants, check out this article: Is Vermicompost Good For Succulents?
How To Use Vermicast for Plants
Vermicast is used much like vermicompost – as a fertilizer for plants. Though vermicast cannot burn plants like other fertilizers, you should not use too much to avoid nutrient toxicity.
You can mix Vermicast with soil, add it as a thin top layer, or make worm tea.
Mixed In With Soil
A good guideline for adding vermicast into your soil is to use it as 20% to 30% of the mix for flowers and food plants. All other bushes, shrubs, and trees should not need more than 20% of vermicast.
If using vermicast to fertilize indoor plants, add a tablespoon for each gallon of potting soil.
When you mix vermicast with other soil, you must consider the nutrient content of the planting media you are adding it to. You should add less vermicast to avoid potential nutrient toxicity if it is high in nutrients.
Learn more about using worm castings in your potted plants in my article here: How To Use Worm Castings in Your Potted Plants?
Top Layer
Adding a layer of vermicast on top of your soil is another good way to utilize it. This method is particularly effective for desert plants because it allows the nutrients to travel to the roots without causing water to pool directly against them.
Your vermicast layer should not be thicker than 1 inch (2 ½ cm) for larger outdoor plants.
For smaller indoor plants, ¼ to ½ inch (¾ to 1 ¼ cm) of vermicast is sufficient. Since the roots in these plants are more shallow, they absorb the nutrients more quickly than their larger outdoor counterparts.
If you choose to add more vermicast later, you should wait at least two weeks. For indoor plants, this additional vermicast should be no more than one tablespoon (15 ml) for every 6 inches (¼ cm) of the pot’s diameter.
Like mixing vermicast with soil, you need to be aware of the nutrients provided by the other planting media you are using. Adding a thinner layer on top of nutrient-filled soil is a great way to modify this method.
Worm Tea
You can make worm tea by soaking worm castings in water, resulting in a liquid full of microbes that you can add as a liquid fertilizer.
One benefit of the tea is that you are not limited to the roots. You can use worm tea on the entire plant, including the leaves. This fertilizer can help keep insects away and prevent diseases that often enter the plant through its leaves.
To use worm tea, you can use a spray bottle or watering can to wet the leaves and soil. If you only use worm tea on the leaves, you do not need to worry about the nutrients in the dirt since the roots would not absorb the tea.
Final Thoughts
Using pure vermicast or pure worm castings can be very beneficial for your plants. The nutrients found in worm castings provide so many nutrients that help your plants stay strong and healthy. However, you must use vermicast in moderation to prevent nutrient toxicity, which is particularly important for desert plants.
You can use vermicast as topsoil, mixed with your other soil, or as a worm tea. Although worm tea is more intensive to make, it provides additional microbes not found in vermicast.
Happy vermicasting!
