Table of Contents
- 1 What is Vermiculite?
- 2 How to Use Vermiculite in Gardening
- 3 Does Vermiculite Contain Asbestos?
- 4 Other Growing Mediums to Consider
- 5 FAQs
- 6 References
What is Vermiculite?
Vermiculite is a hydrous mineral that can be added to soil to improve its conditions.
Vermiculite forms due to the weathering of phlogopite or biotite and undergo a notable expansion when heated.
In layman’s terms, it’s a rock that has gone through changes through heat, weathering, and pressure.
Since this weathering process takes place in nature, it is called a naturally occurring mineral.
It also appears in rocks like mafic, ultramafic, felsic, carbonatites, limestone, serpentine, talc, chlorite, and apatite.
Fun fact: Did you notice vermiculite is similar to vermiculture (which is composting by using worms).
The reason vermiculite gets its name is because when it is heated, the material resembles small worms as it expands.
Both vermiculite and vermiculture are related as they originate from the Latin word vermiculare – which means ‘to breed worms’.
You can purchase Vermiculite of different grades and sizes.
Vermiculite is so versatile that if you plan to germinate seeds, the tiniest size of vermiculite can be used.
Different sizes of it can be mixed to make a growing medium – especially as a hydroponics growing medium.
At the same time, larger sizes can improve soil aeration.
In addition, it has a neutral pH, which is non-toxic to plants.
Vermiculite Mineralogy: Two Types
There are two types of clay minerals:
i) 1:1 type
ii) 2:1 type clay mineral.
The type is determined by its structure and the position of the Silicon tetrahedral and Aluminum octahedral sheet.
Specifically, 1:1 type minerals have one tetrahedral and octahedral sheet, while 2:1 type clay minerals have one octahedral sheet sandwiched between two tetrahedral sheets.
As a 2:1 type clay mineral, Vermiculite has a higher cation exchange capacity (CEC) than other minerals, indicating better nutrient retention.
Also, it has a shrinking and swelling capacity.
Due to all these surface characteristics, expanded Vermiculite can improve soil structure, retain moisture, and can be mixed with other raw materials, potting mix, and perlite.
How to Use Vermiculite in Gardening
Plants require soil to grow as it provides oxygen for respiration, water, and nutrients for growth.
Vermiculite increases the water retention capacity of garden soil.
Due to its higher moisture retention and CEC can retain nutrients and release them when necessary, boosting the plant’s growth.
If you ever notice that the condition of the soil structure in your garden is not good, you can add Vermiculite.
As an aside, it can be a great addition to the lawn as it is advantageous for the lawn’s soil.
Below is a list of various uses of vermiculite in gardening.
- Exfoliated Vermiculite, produced by chemical or thermal treatment  can be used as a soil amendment to enhance potting soils.
Using it will accelerate the plant’s growth in potting soil. It can also be mixed with compost or peat soil to help promote root growth.
- Using this mineral as a growing medium can enhance the absorption of potassium, ammonium, magnesium, calcium, and trace amounts of micronutrients to accelerate the growth.
- Medium grade particles can be utilized for root cuttings directly.
Simply insert the cutting in the medium up to the node. It encourages plant roots to grow.
You can also try growing root crops in it.
- The finer grades of Vermiculite can boost the seed germination rate.
If you use it without soil, you need to use a weak fertilizer solution to feed the seedlings.
15ml of the solution should be mixed with 4L of water, or the concentration may become too strong.
- Mixing it with other materials can provide excellent aeration in your garden soil.
As a result, earthworms and other beneficial microbes will become happier.
Vermiculite acts like a sponge, and it can absorb more water than perlite. Thus, it can absorb excess moisture present in the media.
- Vermiculite can be used for planting flowers as it can accelerate the bloom and keep it fresh for a longer duration.
- Vermiculite can prevent root rot that may kill the seedlings.
Does Vermiculite Contain Asbestos?
Horticultural Vermiculite sold in the stores does not contain asbestos.
In the past, however, it contained asbestos, which is obviously not good for gardening purposes.
You may face asbestos-related diseases if you use that type of Vermiculite. In some parts, like attic insulation, you may still find this.
However, to be clear, in current times, vermiculite does not contain any asbestos.
Asbestos is a long, strong, thin, and flexible mineral fiber.
Before it was discovered that it causes cancer, asbestos was added to building materials to make them strong, fire-resistant, and provide thermal resistance against high temperatures.
It is a lightweight aggregate, which makes it easier to handle in construction.
Since asbestos fiber was associated with illnesses in humans , vermiculite insulation has been banned in many countries.
Other Growing Mediums to Consider
Vermiculite, when mixed with perlite and compost, can increase the soil’s water retention capacity.
Perlite, another type of mineral, can be used in combination with vermiculite.
Related post: Differences Between Perlite vs. Vermiculite
You can also use it in relatively heavy clay soils to supply essential nutrients.
Vermiculite can improve the percentage of the seed germination rate and the growth of plants roots.
Related post: Other Types of Growing Mediums in Gardening
Is Vermiculite safe to use for planting?
Yes, it is safe to use. A mixture of large and fine particles can ensure better drainage to the soil.
It can also prevent nutrient loss due to its higher CEC.
Are perlite and Vermiculite the same mineral?
No, they are not the same.
Though both of them are good for gardening, perlite works best for heavy soils.
Is it dangerous to use Vermiculite?
No, but make sure that the mineral does not contain asbestos fiber.
 Valaskova, M. and Martynkova, G.S. (2012). Vermiculite: Structural Properties and Examples of the Use. Clay Minerals in Nature – Their Characterization, Modification, and Application.
 Addison, J. (1995). Vermiculite: A Review of the Mineralogy and Health Effects of Vermiculite Exploitation. Regulatory Toxicology and Pharmacology, 21(3): 397-405.
Lindsey Hyland grew up in Arizona where she studied at the University of Arizona’s Controlled Environment Agriculture Center. She continued her gardening education by working on organic farms in both rural and urban settings. She started UrbanOrganicYield.com to share gardening tips and tactics. She’s happy to talk about succulents and houseplants or vegetables and herbs – or just about anything in a backyard garden or hydroponics garden.