There are so many options when it comes to substrates for your plants. Although they may seem comparable, each material is unique. Vermicast and vermiculite are no exception.
Vermicast is the worm castings produced by vermicomposting used as a fertilizer rich in minerals and nutrients. It can be used as topsoil, mixed with other soils, or as a worm tea. Vermicast is a more refined version of vermicompost.
Vermiculite is a naturally occurring clay mineral used as a substrate alongside or in place of soil. It often comes in little, curly pellets but can be ground down further. Due to its lightweight structure, it can retain water, allow for better drainage, and provide the soil with more oxygen.
In this article, I’ll explore the differences between vermicast and vermiculite. You’ll also learn how to utilize both to improve your soil and strengthen your plants.
Vermicast vs. Vermiculite: Similarities and Differences
Vermicast comes from vermicomposting, a system where redworms are fed waste such as kitchen scraps or animal waste. As the worms process the material, they add many essential nutrients. The castings they excrete are then collected and used as fertilizer.
Vermicast is a more refined version of vermicompost but contains the same nutrients and benefits in a more concentrated form. Since it has so many nutrients, it cannot be used alone and must be mixed with other soils or growing mediums.
The terms vermicast and vermicompost are often used interchangeably, but there are some slight differences.
On the other hand, vermiculite is a natural mineral often used as an alternative plant substrate or amendment to soil. It is an excellent choice for cuttings to help them establish roots before being placed in soil.
With these in mind, let’s explore the similarities and differences between these two gardening materials.
Similarities: Excellent Water Retention and Neutral pH
Vermicast and vermiculite are both great at holding water and have a neutral pH. Water retention allows plants to access water longer, and a neutral pH allows them to absorb all of the nutrients they need.
Vermiculite can store 4 to 5 times its weight in water, while vermicast can hold up to twice its weight. Due to their absorption and aeration, they can keep water near the roots of your plants, allowing your plant to absorb water when they need it.
It also means you don’t have to water the plants as often. This is very helpful in hot climates, where water evaporates quickly. However, they are not suitable for desert plants like succulents and cacti, which can be negatively affected by soils with good water retention.
Both vermicast and vermiculite have a neutral pH of 7. This is important because most plants require a pH between 6 and 8 (although there are a few exceptions, such as blueberry bushes, which prefer a lower soil pH). Soil pH is important because plants can only absorb certain nutrients at specific pH levels.
For example, plants can’t absorb potassium at a pH above 7.5, and magnesium levels drop significantly under a pH of 6.
Maintaining a neutral pH provides an environment for all of the necessary nutrients to be available.
Differences: Nutrients, Use, Production, Microbes, and Odor
Vermicast has many nutrients, has a wide variety of usages, and is possible to make at home. On the other hand, vermiculite doesn’t contain any nutrients, pathogens, bacteria, or odor.
Perhaps the most significant distinction between the two materials is the nutrient content. Vermicast is filled with nutrients that plants need to flourish.
These nutrients result in:
- Stronger plants
- More flowers or produce yield
- Brighter flowers
- Faster plant growth
Vermiculite, on the other hand, has no nutrients at all. Although vermiculite has no nutritional properties, it can assist in the absorption of nutrients from other sources, including magnesium, potassium, and calcium.
Vermiculite can be used on its own to help transfer plant cuttings to the soil, but aside from that, its primary function is to provide drainage and cannot be used alone with plants. This means you can combine vermicast and vermiculite without the risk of nutrient toxicity.
If you haven’t heard of the term “nutrient toxicity” before, it means the plant essentially suffers from an overabundance of certain nutrients. Like humans, plants cannot handle excessive amounts of certain nutrients without suffering from some form of disease or disorder.
Vermicast is a fertilizer used in addition to soil. You can use it as a top layer, worm tea, or mix it with the soil. (These methods are discussed further in my article “Is Vermicompost Good for Hibiscus Plants?.”) On the other hand, vermiculite isn’t quite as versatile.
The best way to use vermiculite is to mix it in with the soil to create pockets of air throughout the soil. This is how it improves water retention and allows excess water drainage. There’s not as much soil in potted plants, so it doesn’t need as much aeration. Instead, you can put a layer on the bottom to allow drainage.
Both vermicast and vermiculite are available online and in gardening sections at most stores. However, some gardeners prefer to make their materials at home to save money and be confident that the ingredients don’t contain any harmful chemicals.
Vermicompost is easy to make at home and requires little space and experience. Although it can take several months to get a worm bin up and running, once your system is established, you can harvest your worm castings more regularly.
On the other hand, vermiculite must be mined, exfoliated, and exposed to severe heat and enormous pressure for it to be suitable for consumer use. This process refines the mineral and gives it the puffy, curly texture we know.
Vermicast is worm waste. This means pathogens and beneficial bacteria will be introduced as the worms process the material. If you use other animal waste to feed the worms, the number of microbes would be much higher so you couldn’t use it as fertilizer for food plants. Unlike traditional compost, a worm bin doesn’t produce any heat, so it cannot kill any microbes.
Vermiculite, on the other hand, contains no microbes (whether beneficial or harmful). During the process of making the vermiculite ore into the final product, it’s exposed to extreme heat. The heat can kill all the pathogens and bacteria that may have been present, meaning vermiculite is entirely safe for use on any food plant.
While neither vermicast nor vermiculite has the strong odor associated with manure and fish emulsion, there’s a subtle difference between the two. Vermiculite has no scent at all, while vermicast has an earthy smell similar to wet soil.
Mixing Vermicast and Vermiculite
Vermicast and vermiculite can be used together. However, they should be used with other substrates, such as soil, cocopeat, or peat moss. When using vermiculite in conjunction with soil, it should make up 10-20% of the potting material.
In a pot, vermiculite should be at the bottom for better drainage. Conversely, when used with garden soil, you can mix it with other soil or materials.
A study conducted by the Bioresearch Technology journal found that vermicompost should make up no more than 40% of a soil mixture. Since vermicast is more concentrated, it should make up even less. I recommend using no more than 30% vermicast in your substrate mix.
As you can see, a portion of the mixture is still unaccounted for.
There are many different materials you can add, including (but not limited to):
- Peat moss
- Potting soil
- Dry bark
If the material you choose to add has a high level of nutrients, you should decrease the amount of vermicast you add to avoid nutrient toxicity.
Vermicast and vermiculite are different, and they each have unique qualities to offer your garden. Although both excel at water retention and have a neutral acidity, vermicast has more nutrients and more options for use. It’s also something you can make yourself.
On the other hand, vermiculite doesn’t have any nutrients, pathogens, or bacteria and is odorless. You also can’t create vermiculite at home.