Both Perlite and Vermiculite are inorganic materials, made by taking materials mined from nature. They expand to create a final product.
They are both used as soil amendments. Such as traditional gardening and as a growing media in hydroponic gardening.
Are perlite and vermiculite the same thing? or are they Interchangeable?
The answer to both parts of that question is, no. They can be in a similar way, but they are not interchangeable.
Table of Contents
What is Perlite?
Perlite is glass found in volcanoes and saturated with water. When heated to 1,600 degrees Fahrenheit it pops like a corn kernel turning into popcorn.
That expansion creates something that is thirteen times larger than the original piece.
Thus, giving you a final product that is a very lightweight material. Per cubic foot, finished perlite weighs only six or seven pounds.
Being it expands due to the water exploding and evaporating, it creates many tiny air pockets.
These hold water on the outside, not inside, which allows the plants to get the water easier. It tends to dry out faster but is reusable.
The color of perlite is white, which is why many people confuse it with Styrofoam.
For more detailed information on vermiculite and its uses, see our post on perlite.
What Is Vermiculite?
Vermiculite is a group of minerals (aluminum-iron- magnesium) that are mined from rocks.
Like perlite, it is also heated to a very high temperature of 1,652 degrees Fahrenheit.
It has very tiny droplets of water in it. Instead of popping, the heat turns it into accordion-shaped, worm-like structures.
These, composed of many layers of thin plates. These particles are anywhere from eight to twenty times larger.
Due to their chemical composition, they are lightweight, odorless, and can absorb water.
The color of vermiculite can range in color from black to shades of brown and yellow or gold and coppery.
For more detailed information on vermiculite and its uses, see our post on vermiculite.
Benefits of Perlite in the Garden
Perlite is good if you have plants in your garden that need the soil to dry out completely between watering.
Say, for example, if you want to grow a cactus and succulents or some other plant that likes it dry perlite would be great to add to the soil.
Perlite allows excess water to drain. It improves soil aeration giving it better drainage.
That allows more oxygen to your plants’ roots.
Benefits of Vermiculite in the Garden
Vermiculite is the opposite of perlite. Used for plants that want the soil to stay more on the damp side and not dry out.
It will absorb three to four times its volume in water, keeping the soil moist and a tad heavier.
Since it acts like a sponge, it does not aerate the soil as much, meaning less oxygen around your plant’s roots.
Be wary of using too much vermiculite, all that extra moisture can lead to root rot.
Being that it retains moisture, used as a cover layer to help seeds germinate without the bed drying out.
Perlite Vs. Vermiculite: What are the Differences
While perlite is great in keeping the soil mix from compacting. Perlite has an alkaline pH between 7.0 and 7.5.
If used too much it can cause minor nutrient issues.
Tying up the fertilizers, most plants prefer more acidic conditions.
Vermiculite has a pH between 7.0 and 7.5, making it more neutral and is better for most plants.
Perlite added to clay soils will end surface crusting and wet spots.
The insulation properties of perlite will maintain soil temperatures.
Horticultural perlite has different grades depending on how you want to use it.
Most general applications can use a fine or medium grade. Considered sterile and free of weed seeds and diseases.
Vermiculite is preferred by many plant professionals for the rooting of cuttings.
It retains moisture and plant foods, releasing them to the cuttings as needed.
Combined with other things such as peat moss, pine bark, or compost, it creates faster root growth.
Thus, providing the young roots with better stability.
Vermiculite, considered permanent, as it will not deteriorate.
It is clean, non-smelling, non-toxic, sterile, and will not get moldy or rot.
perlite vs. vermiculite: Which One is Better?
Both have been around for many years as soil amendments.
They both also have been used extensively in the world of hydroponics.
Both perlite and vermiculite are a great compliment to each other.
In hydroponics, the growing medium, such as the perlite or vermiculite, takes the place of the dirt or soil.
Not by providing the nutrients.
That is what the water flow does. It is so the roots will support the weight of the plants and hold it straight up.
Perlite is used by itself, though rarely, because of its lightweight.
The downside in certain hydroponic systems the water interacts with the growing media.
Thus, shifting it around too much and could wash it away.
It is much better as a mixture with other mediums, like vermiculite.
A mixture of 50 – 50 is a very common scenario, you will want to use the large grade perlite, a size #3 or #4.
Perlite also has good wicking action which for a wick-type hydroponic system is ideal. Perlite is also cheap and easy to find.
There are a couple of drawbacks to perlite in hydroponics. It retains water and moisture well. Further, perlite dust is not healthy to breathe in.
Considered a nuisance, perlite dust will bother your eyes, throat, and lungs.
You should always wear some kind of a dust mask when using a lot of it.
How to Mix Perlite and Vermiculite
Here is how the two work so well together. Vermiculite retains moisture. Perlite doesn’t.
Use that 50-50 mixture as a growing medium in your drip-type hydroponic system as well as an ebb and flow type system.
It will keep the water and nutrients and still supply the roots with plenty of oxygen.
Vermiculite is also cheap but tends to be a little harder to find.
There is one major drawback of vermiculite.
It retains so much water, that if it is used on its own, it may suffocate the roots of the plants grown in it.
Other Growing Mediums to Consider
You should now understand the difference between the two.
Both perlite and vermiculite can improve your soil conditions, such as aerating your soil, improving water retention or lack of.
They are both used in gardening, especially in the aquaponics and hydroponics industry, however, remember, perlite and vermiculite are not interchangeable.
Related post: Pumice vs. Perlite: When Do You Use Them?
We hope this post will be helpful when you are looking for your next soil additive or hydroponic medium.
For other ideas on what type of growing mediums to use in your gardening, check out our related post on other types of hydroponic growing mediums.
- Verlardo, M. (2017). What Is Perlite?. Sciencing.com website.
- White, A. (2017). What Is Vermiculite? Sciencing.com website.
- Damrosch, B. (2014 March 26). Get to know your potting mix: Vermiculite and perlite. The Washington Post.
- UGA Extension Publications. (2015). Essential pH Management in Greenhouse Crops: pH and Plant Nutrition. The University of Georgia, UGA Extension.
- Maxim, L. D., Niebo, R., & McConnell, E. E. (2014). Perlite toxicology and epidemiology–a review. Inhalation toxicology, 26(5), 259–270.
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.