Download quality criteria Expanded Clay Granules as Growing Media

 Expanded Clay Granules as Growing Media
(RAL-GZ 250/04 – quality criteria 2018)

Quality criteria for expanded clay granules

RAL-certified expanded clay for use as a growing medium

Expanded clay is produced by heating high-quality natural clay with expansion additives in a rotating kiln to 850 and 1,200 °C. This treatment causes the clay granule volume to expand to a multiple of its original size. Originally, expanded clay granules were feedstock used in the construction industry. Due to their special properties, expanded clay granules are now used in numerous applications in gardening and landscaping. A special extraction method and testing schedule for expanded clay granules (developed at the Institut für Bodenkunde und Pflanzenernährung [Institute of Soil Science and Plant Nutrition] at FH Weihenstephan) ensure that plants tolerate the material.

Applications for expanded clay granules in landscape gardening:

  • growing media in cutflower and vegetable production
  • hydroponics substrate for interior landscaping
  • constituent for substrates for green roofs

Expanded clay granules are ideal for use in landscape gardening because they offer the following benefits:

  • light weight
  • stable structure, no decomposable constituents
  • large exterior and interior surfaces that facilitate water films to form
  • low salinity