Vermiculite vs Perlite
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January 19, 2021
- Posted by: Citizen Cooling Solutions Limited
Vermiculite vs Perlite
What is perlite?
Nicknamed “volcanic popcorn,” perlite is made by heating volcanic glass to super high temperatures until it expands and “pops” into the white, porous, lightweight rock that resembles little Styrofoam balls.(Despite similarities in appearance, Styrofoam should never be used in gardens or as a substitute for perlite.) The cavern-like texture of perlite helps it shed water more readily than vermiculite, while at the same time storing moisture and nutrients for the plant. These qualities are what make perlite so good at providing oxygen to plant roots and improving soil structure.
What is vermiculite?
Like perlite, vermiculite is a naturally occurring mineral that expands when heated. Scientifically speaking, it’s the name for a group of hydrated magnesium iron aluminum silicate minerals (phyllo-silicates) that look like shiny, silvery gold to grayish brown flakes. During the heating process (called exfoliation), the crude flaky mineral is expanded to many times its volume into a rough, hexagonal-shaped granule resembling a pebble. These chunky granules are further processed into the coarse, medium, and fine grades of vermiculite that we see and know in gardening.
Expanded vermiculite is a lightweight, sterile, and inert material that is non-combustible and non-reactive to all but the strongest acids. It’s also non-toxic and safe to use in a variety of applications.
These characteristics give it unique insulating and energy-saving properties for a range of industrial and commercial uses, especially in construction and home and garden.
Vermiculite is used for special coatings and packaging, fire protection, loose-fill insulation, concrete screeds and plasters, swimming pool liners, and potting mixes or potting soils. It’s the same material used in gas fireplaces with ceramic logs to help the flame spread across the burner more evenly.
For horticultural use, vermiculite is found in four different grades, or granule sizes:
| Type of Vermiculite | Grade | Granule Size |
|---|---|---|
| Super coarse vermiculite | #4 | 4mm to 8mm |
| Coarse vermiculite | #3 | 3mm to 6mm |
| Medium vermiculite | #2 | 2mm to 4mm |
| Fine vermiculite | #1 | 1mm to 3mm |
Does vermiculite contain asbestos?
The short answer: no.
If you’re buying horticultural vermiculite sold in stores today, then that vermiculite does not contain asbestos.
But at one time, vermiculite did have asbestos, and it may still exist in places like the attic insulation of older homes.
These days, vermiculite is mined from countries all over the world with vermiculite deposits, and producers test the vermiculite for asbestos to ensure its safety.
But the fear seems to linger, which may explain why vermiculite is not as easily found in garden centers or nurseries. If you have trouble sourcing it locally, reach us today to get them.
Perlite vs. vermiculite: How do you know which one to use in the garden?
Like perlite, vermiculite is an effective soil conditioner that can loosen compacted soil, provide drainage, and hold three to four times its weight in water.
But — and this is an important but — vermiculite is more compressible and less porous than perlite, giving vermiculite higher water-holding capacity when it’s used as a planting medium.
Vermiculite acts more like a sponge in the way it soaks up water and holds on to it. Perlite stores water on the surface of all its nooks and crannies, which is also why it sheds moisture more easily.
Use perlite if:
- You want to loosen heavy clay soil. Perlite helps break up surface crusts and reduce soil compaction.
- You’re re-potting houseplants or plants that like to stay on the drier side. Shade-loving houseplants, succulents, and cacti do better with less water, so a potting mix amended with perlite helps prevent root rot and fungal disease.
- You garden in a wet or humid climate. Adding more perlite to containers or garden beds helps keep the soil from becoming waterlogged.
Use vermiculite if:
- You’re starting seeds. Because vermiculite holds moisture better than perlite, it helps keep seeds from drying out during germination.
- You’re re-potting outdoor container plants. Potted plants tend to dry out faster outside, especially if they’re in porous containers like terra cotta or fabric pots. Adding vermiculite to your potting mix helps them retain moisture better.
- You garden in a dry climate. Adding more vermiculite to potting soil and soilless mixes conserves moisture in the growing media.
Remember this general rule of thumb:
Use perlite when you want better drainage and aeration.
Use vermiculite when you want more moisture retention.
Call us today on 0724 381 416 to place your order.
