The Spruce / Jason Donnelly
Novice gardeners sometimes confuse vermiculite and perlite.
However, vermiculite is used to improve water retention, while perlite is used to increase drainage.
In some cases, there may be little harm in using these materials interchangeably.
The Spruce / Jason Donnelly
Here’s how vermiculite and perlite differ, and how to know when to use each.
What Is Vermiculite?
Vermiculite is a silvery-gray, flaky materialsold by the bag at home improvement stores.
The Spruce / Jason Donnelly
A popular size is 2 cubic feet, which is somewhere between 10 to 20 pounds when dry.
Vermiculite is mined from the earth in its raw form.
It is then exfoliated and subjected to extreme heat and pressure.
The Spruce / Jason Donnelly
This treatment both sterilizes it and forces it to expand.
The result is a clean, fluffy product that can serve a number of functions for gardeners.
Vermiculite also contains minerals that are helpful to plants, although it does not contain any added fertilizer.
The Spruce / Jason Donnelly
But vermiculite isn’t just for growing things.
It’s also easier for seedlings to break out of a layer of vermiculite than a layer of soil.
Plus, the sterility of fresh vermiculite ensures you aren’t exposing your seed to pathogens.
What Is Perlite?
After this treatment, it becomes a gardening product valued as a soil amendment.
But its appearance is distinct from that of vermiculite: Perlite is white and chunky.
Even its texture is different: Perlite feels like styrofoam.
Perlite is sold in bags at home improvement centers.
Common sizes are 2 cubic feet and 4 cubic feet.
Professional growers buy perlite wholesale in larger bags, but these can be a bit bulky for the consumer.
A bag that is 2 cubic feet weighs about 8 to 16 pounds when dry.
The 4 cubic feet size is more manageable in this case than with vermiculite.
The difference in weight comes from the fact that perlite is airier than vermiculite.
This airy quality furnishes a clue as to its uses.
Uses for Perlite
Its airiness gives plant roots greater access to oxygen and promotes drainage.
It is used as a soil amendment both for containers and planting beds.
Can You Use Vermiculite and Perlite Interchangeably?
Both help retain water, but they do so in different ways and to different degrees.
Vermiculite absorbs it like a sponge.
Its flakes actually expand when it sops up water.
Of the two, vermiculite does a much better job of retaining water.
In planting beds, it’s a great choice for sandy soils, which lose water rapidly.
Perlite excels in aeration.
So use it as a soilless potting mix for plants that aredrought-tolerantand require superb drainage, such ascacti.
For certain garden tasks, you may very well end up using both vermiculite and perlite.
Which Medium Should I Use For My Garden?
Use Vermiculite if…
Use Perlite if…
Both vermiculite and perlite are nonrenewable resources that are mined from the earth.
There are many options toamend your soilto help retain water and improve drainage in place of vermiculite and perlite.
For water-retaining properties, try bentonite clay or coconut coir.
Well-decayed sawdust or rice hulls are both good for water retention and drainage.
One medium is not better than the other.
They simply have different purposes.
Additionally, vermiculite can be quite dusty and is a non-renewable resource.
Also, some plants need soil that retains consistent moisture and doesn’t dry out.
Vermiculite Insulation.Minnesota Department of Health.
I use/used vermiculite to enhance my potting soil.
Should I be concerned?United States Environmental Protection Agency.
