It is not unusual to become confused between perlite and vermiculite when you go to the garden center or online to buy them. While they are both used as growing media, they have different roles to play. One (vermiculite) holds water well, and the other (perlite) does not, but is good at creating drainage and aerating the soil.
When it comes to horticultural uses, telling them apart is easy, because they look so completely different. Vermiculite is brown with a soft and spongy texture. Whereas Perlite is sold as tiny hard white balls, similar in appearance to tiny Styrofoam balls used for packaging.
Many hydroponic growers use both vermiculite and perlite as a growing media because it can be used effectively without soil.
- 1 Vermiculite and Perlite for Gardening Use
- 2 What is Vermiculite?
- 3 What is Perlite?
- 4 Where to Buy Perlite
- 5 Using Vermiculite and Perlite Together
Vermiculite and Perlite for Gardening Use
In this article, we take a close look in detail at both Vermiculite and Perlite. We explain when to use them, why to use them, and consider the safety issues around these plant growth mediums. In the end, you’ll likely find that both have a place in your potting shed!
Now let’s have a look in closer detail at both Vermiculite and Perlite, and see what benefits these versatile horticultural aids can have in your garden.
What is Vermiculite?
Vermiculite is a hydrous phyllosilicate mineral ore.
What now? What does that mean?
- Hydrous = An element that can absorb water
- Phyllosilicates = Sheets of silicates
- Mineral = Natural inorganic chemical compound.
Essentially, Vermiculite is a medium that helps plants absorb liquids, like water.
Vermiculite consists of hydrogen, magnesium, iron, aluminum-silicon, and oxygen. When heated, it expands into a lightweight, chemically non-reactive material. The porous texture makes it ideal for soaking up liquids, such as insecticides and fertilizers.
Many hydroponic growers use it as a medium for growing.
Because it is a natural fire-resistant element, it is also used as an additive to some building materials.
Where does Vermiculite Come From?
Vermiculite is mined in many places around the world, from open cast mines. It comes out of rocks that consist of biotite and iron-bearing phlogopite (mineral). When rocks become exposed to the climate, they decompose. This allows water to leak inside. The water then reacts to other chemicals present and forms vermiculite.
There are many industrial-scale mining sites in South Africa, Russia, Brazil, and China.
Is Vermiculite a Rock?
No, although the mineral is extracted from mined rocks. It is actually 2:1 clay. The mineral structure consists of 2 layers of tetrahedral for each layer of octahedral, lending it the unique properties. The huge rocks are crushed into smaller pieces. Only then can the vermiculite inside become separated.
In its raw material state, once mined, Vermiculite looks like crystalized layers packed tightly together to resemble a shiny crystal rock.
Where does it get its name from?
It is a Latin word and comes from “vermiculture” which is the use of worms for decomposing organic waste. Once heated, the mineral turns into long strands, that are similar to worms.
Hence the name.
Unseen, but between the platelets, is a hidden collection of water. When the mineral reaches high temperatures in a furnace, the trapped water turns to steam. This causes the platelets to expand. At this point, the mineral changes color. The process is called the exfoliating stage. Later it will be further graded into varying sizes, such as fine, medium and course. Some customers request the mineral to be ground into a powder.
When complete, it is then shipped to commercial buyers.
Is Vermiculite Safe to Use?
You may have heard stories that vermiculite contains asbestos. Before 1999 this was true, but it no longer is.
From the beginning of the 20th century until the late 1990’s, mines in Libby, Montana, sourced 80% of the world’s vermiculite. They also mined asbestos, which contaminated the vermiculite.
Once it became known that asbestos was dangerous, strict protocols were set in place. This resulted in no more cross-contamination. Now, all vermiculite sold is free of asbestos.
In 2000, a report from the US Environmental Protection Agency (EPA) helped to ease customer worries. They stated that vermiculite sold for agricultural purposes proved no risk to consumers with regards to asbestos contamination.
While it is safe to use, there a few precautions you can take if you are still worried:
- Look for bags of vermiculite labeled “non-dusty,” to avoid dealing with any fine dust.
- Only use in a well-ventilated area.
- Apply to soil on non-windy days, and wet the soil once completed.
- Cover your mouth and nose when using it, if you are still concerned.
Horticultural uses for Vermiculite
One of the most popular uses is within horticulture. Before it can be used for growing crops, it is treated and sterilized. Again, it has many valuable uses:
- Added to soil or peat, it speeds up germination of seeds. It’s helpful to get an early start on the season, combined with a mini greenhouse!
- Medium grade can be used successfully on its own, for root cuttings.
- Added to potting soil, it not only aerates well, but it is also good at maintaining water and nutrient levels.
- Great for container growing too, as it makes the soil aerated and fluffy, with good drainage.
- Ideal to use in planting baskets because it is lightweight, with good drainage.
- Popular in hydroponic growing as a lightweight medium. Not only can it retain water, but it naturally drains it away once fully expanded. This stops plant roots from drying out.
- Great for spreading over newly laid lawns. Improves the soils aeration and water retention, which aids germination.
- Added to vases of flowers, your blooms will stay fresher for longer.
- If planting outdoors, once you have dug the hole, pop some vermiculite in the bottom for added aeration and drainage.
- Added to many composts, you will see it as the shiny grey-silver bits. You can also safely add it to your own home-grown compost pile.
- As a rule, the finer the grade is better for the beginning stages of a plant. The bigger the grade, the mineral is better to go into the soil to break it up.
- Vermiculite is odorless.
Commercial Uses for Vermiculite
Once processed, vermiculite can end up in a variety of different industrial processes. It is highly valued in this sector for its fire-retardant qualities and used in many ways, such as:
- Added to insulation material.
- Being pressed and added to plasterboards.
- The automotive industry uses this mineral to line brakes. Many years ago, breaks were lined with asbestos.
- Added to plaster, it makes the plaster more efficient. Not only does it make the plaster fire resistant, but also less susceptible to damage, such as cracking or chipping.
- Added to cement for curing purposes, as it helps to keep moisture in. Makes for a lightweight concrete that does not dry out before it is fully used.
- Modern firebacks are often constructed from vermiculite firebricks.
Where to Buy Vermiculite
- Home Centers and Garden Stores often sell the smaller bags, which can end up costing more.
- Local nurseries or farm shops may sell the bigger bags of around 100L, making it more cost-effective.
- Vermiculite is easy to find online in places such as Amazon. The brands we have featured in this article can be found below.
Last update on 2019-02-20 / Affiliate links / Images from Amazon Product Advertising API
What is Perlite?
As a raw material, perlite is a volcanic glass, a form of obsidian, with a high-water content. Just as there is man-made glass, nature also has its own way of producing glass. Certain minerals that form in volcanic molten rock turn into perlite when they come into contact with water.
The water cools the molten rock at a rapid rate, trapping the water content inside. The outside is a hard and brittle glass-like rock. It will need further treatment before it becomes the perlite we use.
Is Perlite a rock?
In its original form, it is a volcanic rock that has developed into a natural glass. Think of it as heating up sugar to form hard boiled sweets, this is a good analogy of natural glass. It is usually found on the very edge of the volcanic lava flow.
When the lava is hydrated and cools, it becomes perlite, trapping water inside which makes it expand. Expanded perlite is usually white or light grey in color.
The chemical composition of perlite includes natural compounds such as aluminum, sodium, potassium, iron, magnesium, calcium and oxygen. Over time this will harden into an obsidian rock formation; known as devitrification. Obsidian is said to be have been discovered by a Roman explorer, called Obsius. At first, perlite was thought useful only for jewelry making, because of its glassy surface.
Where does Perlite get its name from?
Perlite is also known as pearl stone. When broken under force, it forms small round pearlescent pieces.
Is Perlite Safe to Use?
It is a nontoxic element, but when it is processed for industrial use it produces a lot of dust. The inhalation of this may cause respiratory problems for some. As with vermiculite, there have been some concerns that perlite may contain asbestos. Various testing methods have shown that perlite does not contain any asbestos. Research in 1994, by Tulane University, concluded that those exposed to the dust will not have any long-term adverse respiratory effects from it.
As with vermiculite, Perlite is lightweight, fireproof, non-toxic and non-hazardous, making both Perlite and Vermiculite versatile minerals.
The varying grades have many different uses. Perlite goes on to be used as insulation, filtration, paints, cement, faux stones, and even animal feed.
Horticultural uses for Perlite
The heating process has made the perlite sterile, so it is safe to use in your garden.
- Unlike vermiculite, it does not hold and retain water. This is because it is more porous, and instead drains water away much quicker. The main advantage of perlite is that it acts as a good media for aerating and draining soil. It is often used in conjunction with vermiculite. They can complement each other well.
- Like vermiculite, perlite helps to germinate seeds quicker. That said, perlite works better with cuttings or seedlings that have sprouted roots.
- It will loosen clay soil, breaking it up as it aerates. Add it to potting soil or coconut coir, and you have yourself a light aerated media.
- Perlite can be used on its own as a growing media. For its draining composition, it is very popular with hydroponic growers. Though you would need to ensure it is kept moist, as it is prone to dry up quickly.
- It is pH neutral, meaning it will not pollute your soil with acidity.
- As a growing media, it is rot free, pest free, and weed free.
- Because it does not decompose, it can be re-used many times, over a few years before you need to replace it. It will need disinfecting between uses to make sure there is no cross-contamination.
- Scatter the finer granules of perlite over your lawn. Is will make its way down to the roots to help with aeration and root growth.
- A course-grade perlite in the soil, allows plant roots to drain and breath. Great for container planting so the soil does not become compact.
Industrial Processing and Use
Perlite is dug out of open-cast mines, either by blasting or ripping, dependant on the perlite density. It is then sent to a grinding mill and put through a “jaw crusher,” until it is about one-inch in size.
When heated to a high temperature of around 1.7000F, the water contained within the glass-rock will vaporize. This causes it to expand up to twenty times its original size. Think of popcorn, which is a similar process. It will then undergo more grinding for the different grades required.
Perlite is mainly used in the construction trade. It is also used in horticulture, as it helps to aerate the soil.
Where to Buy Perlite
See the “where to buy” in vermiculite. They can be found at similar locations, such as garden centers and online stores.
Amazon carries many brands of Perlite, such as the ones shown here.
Last update on 2019-02-20 / Affiliate links / Images from Amazon Product Advertising API
Using Vermiculite and Perlite Together
Perlite and Vermiculite essentially complement each other when used in gardening, and both materials have their place.
One of the most common methods of using these materials is to start your seedlings with Vermiculite. The vermiculite environment will encourage rapid germination and growth, at which point it’s time to move them over to perlite.
Once you have grown your seeds in the vermiculite, then move them over into a pot of finer perlite. They will develop quickly grown this way, until they are ready to plant out in your garden.
You can choose to use both vermiculite and perlite together, as they complement each other well.
They do play different roles in the soil; one to hole water and one to drain excess water away.