Where in the World: Vermiculite

Published on April 11th 2018
Vermiculite is a mined mineral that when heated expands to thousands of times it original size. It is mined in:
  • Russia
  • South Africa
  • China
  • Brazil

What is Vermiculite

Vermiculite is a hydrated magnesium aluminium silicate mineral which resembles mica in appearance.
Horticultural vermiculite is processed with massive heat which expands it into accordion shaped pellets composed of multiple layers of thin plates.
It will not rot, deteriorate, or gather mould and is enduring, odorless, non-toxic and sterile.
Vermiculite is generally a neutral 7.0 It is very lightweight and mixes easily with other mediums.
Vermiculite is mined using open cast mining techniques where the ore is separated from other minerals and then screened or classified into several basic particle sizes. These have different uses within horticulture.
Vermiculite, when subjected to heat, exfoliates to form elongated concertina like particles which are lightweight, incombustible, compressible, highly absorbent, and non-reactive.
Exfoliated vermiculite particles can have high cation exchange capacity.
Note: Cation exchange capacity (CEC) is the total capacity of a soil to hold exchangeable cations. CEC is an inherent soil characteristic and is difficult to alter significantly. It influences the soil's ability to hold onto essential nutrients and provides a buffer against soil acidification.

How is vermiculite used in horticulture

When I first started in horticulture I really wondered why you would need vermiculite, but as my career and knowledge increased I fully understand that it has an important job to do.
Firstly in seed sowing vermiculite warms up the compost evenly and retains the temperature gained- this means that there are fewer fluctuations meaning a quicker and higher seed germination rate.
Another great thing about vermiculite is that it allows light to travel through it, so seeds that need light to germinate will. Such as Lobelia and Petunia’s the seed packet will tell you they need light and to sow on the surface of the compost and not to cover.
The only problem with this method is that the seeds can dry out easily and die, using vermiculite will keep the seeds in place while you transport the tray to the greenhouse and maintain moisture around the seeds/seedlings.
Plant propagation mixing vermiculite with compost will retain moisture, increase nutrients and heat to help developing roots form. Although perlite is better if used with cuttings that do not need additional water retention. So use vermiculite for water loving plants. Using vermiculite as growing medium will also enable the plant to more easily absorb the ammonium, potassium, calcium and magnesium necessary for vigorous growth.
Propagation units if you lay a bed of vermiculite onto heated cables to make a propagation unit this will reduce the heat loss and retain a constant bottom heat which in turn will increase the vegetative propagation success.
So all in all using vermiculite is not a sales gimmick but a well kept horticultural secret, those who know would put it on their desert island essentials. Give it a try and see if you see the improvements to your horticultural successes.

Do you use Vermiculite? Share your stories with the Candide Community.

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