Perlite vs Vermiculite, What’s the Difference? Don’t Kill Your Plans By Using The Wrong One!

perlite vs Vermiculite

When looking at soil mixtures, you can see there are small pellets gathered in the soil. Those are not compost, soil, or other organic materials. In fact, those small pellets are either perlite or vermiculite, which are added to the plants for better aeration and to keep moisture.

They are also very lightweight, which can help lighten the soil. Perlite and vermiculite are two commonly used inorganic soil additives for gardening. Both of them are natural materials, so many people are unable to differentiate between the two.

In fact, perlite and vermiculite have very different appearance and their properties as well as usage varies. Now, let’s learn more about these helpful materials before you manage your garden.

What is Perlite?

perlite

Perlite is made of a particular type of volcanic glass that has a high water content. This unique type of volcanic glass is formed when water is in contact with obsidian. Such volcanic material contains a lot of silicon, making it perfect for molding.

Manufacturers typically apply heat to perlite, turning them into lightweight, little white balls that look like foam balls. Perlite is clean, odorless and easy to use.

What is Vermiculite?

Vermiculite

Vermiculite is made of mica, which gives it a similar texture. It is spongy and may appear in different shades of brown - ranging from dark brown to golden brown.

There are 19 different varieties of micaceous minerals that form vermiculite and its ores contain silica, iron oxides, magnesium oxide and alumina.

The Differences Between the Two

Physical Properties

Perlite is composed of white and porous granules, which is often mistaken as Styrofoam balls. Not only that, it also has sharp edges. Vermiculite, on the other hand, is composed of brown granules and are soft, spongy and shiny.

Chemical Composition

Perlite is obtained from an amorphous volcanic rock, so it contains a lot of silicon. When it is heated and crusted, the particles will expand and those microscopic bubbles inside of the perlite particles will be able to keep air and water.

As mentioned, vermiculite is made from an aluminum-iron-magnesium silicate called mica. The particles of vermiculite can be expanded by heat, allowing it to hold more water than its original volume.

Manufacturing Process

Perlite and vermiculite ores are heated to create the products we see in stores. For perlite, the crushed ore is heated to around 1470 to 1560 degrees Fahrenheit, making water particles expand up to 15 times its initial volume.

Afterwards, it then turns into a round glass bubble inside the particular. This expansion process is possible due to the presence of around 6% water presented in the rock. As for vermiculite, it can be expanded 8 to 20 times in volume when heated to 1470 to 2010 degree Fahrenheit.

This heating process will cause water to escape from the particular in the form of steam as an exfoliation process.

Water Retention

Both perlite and vermiculite are great agents for retaining water. The surface area of a perlite is larger than a corner and there are cracks in the perlite for water storage. Also, its porous ability helps plants drain excess water for better aeration.

Vermiculite also retains water and it works as a sponge. While vermiculite is able to hold more water, it allows less aeration for the plant root when compared to perlite.

This water retention property is the most well-known difference between perlite and vermiculite. It is important to know that perlite does not absorb water, while vermiculite does. However, what perlite does is increase drainage.

Aeration

Perlite and vermiculite contain spaces in the particles for better aeration, allowing the root of the plant to take more oxygen. In terms of porosity, perlite has a high air porosity and vermiculite is identified as having medium air porosity.

As a lightweight particle, perlite also prevents other organic ingredients from compacting one another.

Read next: How to aerate your lawn

pH Value

Perlite has a slightly alkaline pH value between 7.0 to 7.5, which might cause fluoride burn on plants that prefer an acidic environment. On the other hand, vermiculite has a neutral pH value of 7.0. Even if the pH value of vermiculite might drop to 6.5 to 7.2, it is still suitable for plants.

Both of these materials are considered chemically inactive, but they buffer the pH value of plants in a different way. Vermiculite has a high capacity in buffering pH value, in which it can increase the pH value of the soil. For perlite, it has a low capacity in buffering pH value.

Cation-exchange

The cation-exchange capacity measures the medium’s ability to keep or attract nutrients, so that the nutrients can be retained for the plants to use in a later stage.

In terms of absorbing cations from the soil and providing the substance to plants, perlite has a very low capacity. On the other hand, the sponge-like vermiculite has a medium cation-exchange capacity.

Addition to Soil Mix

No substance or chemicals will be released to the soil when you add perlite. However, adding vermiculite to your plant will make your plant healthier. This is because nutrition such as phosphorus, potassium and calcium will be released to the soil mix.

Seedling Purpose

Both perlite and vermiculite can be used with seedlings. Vermiculite can protect the seedling from being ruined by fungus, while being able to retain water in the pots at the same time.

For perlite, it can be used with seedlings as well, but it is advised that the seedlings are separated into different pots for drainage.

Ideal Use in Gardening

Perlite is best used for plant cutting because of its water drainage properties, while vermiculite is perfect for planting seeds and seedlings as well as plants that require a lot of water.

Other Usage

Perlite is used as a filter for chemicals, food products and water in the industrial process. Another use of perlite is as an insulator for the making of bricks and molar. It can also be used as an abrasive for soaps. For vermiculite, it is used in fireproofing and fungi cultivation.

Grades

The different spectrum of sizes is referred to as grades for the particles. For fine perlite, the particle sizes are around 0.5mm to 4.9mm with 40% to 50% water holding capacity. Medium perlites are around 1.0mm to 4.0mm, with 30% to 35% water holding capacity.

Coarse perlites are around 2.0mm to 8.0mm, with 29% water holding capacity. As for vermiculite, the particle sizes for fine vermiculite are 1.0mm to 3.0mm, with 40% to 50% water holding capacity.

Medium vermiculite is about 2.0 to 5.0mm with 35% to 40% water holding capacity, while coarse vermiculites are 5.0 to 10.0mm with 30% to 35% water holding capacity

When to Use Them

While both perlite and vermiculite can improve aeration and retain moisture, using these materials wrong will harm or even kill the plant.

Using Perlite

Water Drainage

For plants that need to be completely dry out between watering, such as succulents, adding perlite to the soil will be helpful. You can also use perlite when you need to loosen the clay soil in your garden. In general, a fine to medium grade is good for application.

Other Uses

Another common usage of perlite is root cutting. Perlite can be used with peat moss and loam soil in a 1/3 ratio. This substance allows for better root formation. When perlite is added to clay soils, puddles and surface crusting can be reduced.

The temperature of the soil will also be less fluctuated. You can also use perlite when you move your seedlings to different pots. Additionally, perlite can be crushed into smaller particles easily for horticultural use.

There are many uses of perlite, including propagation, plug production, composting, seed cultivation, interiorscape, hydroponic culture and landscaping.

Using Vermiculite

Water Retention

Vermiculite are perfect for plants that need a lot of water, such as forget-me-nots. If perlite is used, the plant will dry out too fast. For plants that grow in well-drained soil, vermiculite is not a suitable choice for the soil.

This is because too much moisture will be captured, which may kill the plant. In that case, perlite should be used. Besides, vermiculite can also help develop strong seedlings. It is possible to germinate seeds with vermiculite alone.

You should apply some weak fertilizer to the seeds, in the proportion of 1 tablespoon of fertilizer for every gallon of water. Additionally, vermiculite is also used for transplanting plants.

It provides moisture and keeps the root spread, hence, preventing the plants from drying under the sun’s exposure.

Perlite vs Vermiculite

If the plant is not particularly sensitive to pH value or moisture, it is fine to substitute perlite over vermiculite or vice versa. One part of peat moss and two parts of either perlite or vermiculite are usually the standard soil mix for vegetables and/or houseplants.

Conclusion

Perlite and vermiculite are both helpful minerals for gardening. They can improve aeration, retain water and prevent the soil from hardening. They are commonly used in the cultivation of seeds and moving new plants.

You will also notice that perlite and vermiculite are used in indoor container composting. Both perlite and vermiculite are safe, effective and easy to use for gardening.

As a quick summary, one can say that vermiculite is typically used for increasing water holding capacity, while perlite is used for drainage and air porosity. At the same time, vermiculite is used for seedings and perlite is better for cutting.

If you are growing something through hydroponics, perlite will be a better choice, or you can do a mix of both perlite or vermiculite. Now, you should have a clearer idea of the differences between these two materials.

Although they may share the same usage, they possess very different qualities. Make sure you understand your plants and what they need before applying perlite or vermiculite so that the roots will not dry out too much or rot.

Featured image thanks to: https://www.urbanturnip.org

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