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What is Perlite?

Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian.

It occurs naturally and has the unusual property of expanding greatly when heated sufficiently.

Why is it helpful to gardeners?

In horticulture it makes composts more open to air, while still having good water retention properties. It therefore helps to make a good medium for hydroponics. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles.

Unexpanded (“raw”) perlite bulk density: around 1100 kg/m³ (1.1 g/cm³). Typical expanded perlite bulk density: 30–150 kg/m³ 

Perfect for hydrophonic systems

Where there is no soil, provides aeration and optimum moisture retention for superior plant growth. For rooting cuttings, 100% perlite is used. Studies have shown that outstanding yields are achieved with perlite hydroponic systems.

Benefits for the home gardener and the commercial grower 

Horticultural perlite is as useful to the home gardener as it is to the commercial grower, it is used with equal success in greenhouse growing, landscaping and in the home in house plants. Some of its benefits include:

  • neutral pH
  • sterile and weed free
  • Lightweight so ideal for use in container growing
  • Can be used as a carrier for fertilizer, herbicides and pesticides and for pelletizing seed


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