Perlite Verses Vermiculite

 

An Explanation of the Differences

By Daniel at DIY Gardening

What is perlite? How is it different to vermiculite? What do these products do, and how are they used?

Are there cheaper alternatives?

This guide is all about perlite v vermiculite, so if you have a question about either, I’m confident you’ll find the answer on this page.

But first…

Please don’t buy either from your local garden centre. 

I checked my two local centres, and the largest bag I could find was 10 litres, and it wasn’t cheap.

You can get far better bulk buy deals online, and both perlite and vermiculite have indefinite shelf lives so there’s few reasons to buy smaller bags.

The Cheapest Online Retailer for Bulk Buys

I’ve trawled the web and these are the cheapest bulk products I could find.

They are advertised as trade bags but are also sold directly to the general public:

Vermiculite 100  litres

Vermiculite Bulk Bag

  • 100-litre bag.
  • Currently sold with free delivery.
  • Over 600 customer reviews.
  • Currently 95% of buyers rate this 4 or 5 stars.
  • Save over 30% compared to buying smaller bags in garden centres.
Perlite 100 litres

Perlite Bulk Bag

  • 100-litre bag.
  • Currently sold with free delivery.
  • Over 2500 customer reviews.
  • Currently 94% of buyers rate this 4 or 5 stars.
  • Save over 35% compared to buying smaller bags in garden centres.

What is Perlite?

Perlite is a type of volcanic glass that has been heat-treated where it then puffs up into small white balls.

Perlite is lightweight, sterile, easy to handle and has no smell.

It absorbs water but is also porous as the water drains freely away.

Perlite is full of air pockets and is primarily used by gardeners to aid with drainage.

Use perlite:

  • In container mixes for plants that require excellent drainage, i.e. a cactus.
  • As a soil enhancer in borders as it will aerate heavy soils.
  • In pots that will be used to grow seedlings as young plants need a loose, well-aerated medium for their roots to thrive.
Perlite

Perlite: Buy on Amazon

What is Vermiculite?

Vermiculite is made from crushed silicate and is yellow/brown in colour; the small flakes will expand when they come into contact with water and can hold up to 4 times their weight in water.

Gardeners often use vermiculite in soil mixes for plants that prefer moist soil, such as hydrangeas.

Many also add it to hanging baskets and pots where there’s an increased chance of the growing medium drying out.

Vermiculite adds weight to the soil as it retains water, something to be aware of if you plan on using it in hanging baskets.

Use vermiculite:

  • In container plants that prefer moist soil.
  • In seed trays as it stops the seeds from drying out (the most common reason seeds fail).
  • In soil that is too light, fluffy and free-draining as it will help it to retain moisture.
Vermiculite

Vermiculite: Buy on Amazon

Vermiculite Verses Perlite: The Key Differences

Vermiculite holds water, increases the weight of the soil and is used to retain moisture.

Perlite aids with drainage and reduces the weight of the soil, it also aerates the mix by holding onto oxygen.

Similarities

Vermiculite and perlite have some similarities as they are both:

  • Inert.
  • Sterile.
  • Contain no nutrients.
  • Have an indefinite shelf life.
  • Do not break down easily in the soil.
  • Absorb moisture (although vermiculite is far better).

Doses

Most gardeners add around 10% perlite or vermiculite to their pot and container mixes.

For plants that prefer the extremes of either wet or well-drained soil, a mix of up to 25% perlite/vermiculite can be used.

In hydroponics, up to 100% of the material can be used provided nutrients are added to the water, but that is outside the scope of our guide which is created for general gardening.

Can Both Vermiculite and Perlite be Used Together?

Yes.

If you have plants that thrive in moist but free-draining soil, you can add both to the mix as they compliment each other well.

Alternatives to Perlite

As perlite is used to aerate and loosen the soil, any of the following can be used as an alternative:

  • Pumice.
  • Horticultural grit.
  • Course horticultural sand.
  • Leaf mould.
  • Finely chopped wood chips.

Alternatives to Vermiculite

There are a couple of alternatives to vermiculite, both help with moisture retention:

  • Peat moss.
  • Coir.

Life Expectancy

Both perlite and vermiculite are derived from rocks, so they won’t rot or decay but can be crushed, split or broken apart into finer particles.

They both have an indefinite shelf life and will persist in the soil.

Perlite floats so will rise to the surface if enough water is applied to the soil. It’s also very light and prone to being swept away in the rain or wind.

How We Use Perlite and Vermiculite

Here at DIY Gardening, we have heavy soil in our borders, but as the garden is elevated, it never becomes waterlogged and generally drains well, so we don’t use perlite or vermiculite in the borders.

We have two hydrangeas in containers and have added about 10% vermiculite to a general compost, this helps to prevent the soil from drying out.

As our hanging baskets are bathed in sunlight, they are prone to drying out so we add vermiculite to our summer baskets (but not our winter baskets).

We also use vermiculite in seed trays and propagation pots to help with moisture retention.

We only use perlite when we transfer seedlings from trays to larger pots as it helps the roots to grow faster and deeper.

Buy Online

More From Daniel Woodley:

This guide to the differences between perlite and vermiculite was created by Daniel Woodley here at DIY Gardening and was last updated on the 21st of November, 2021.

Discover more helpful hints and tips from Daniel over at the blog.

Daniel is a keen amateur gardener who also manages a large residential landscape in addition to his own mid-size garden.

He also enjoys growing vegetables and fruits as well as his herbaceous border and container garden.

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