Quality criteria for potting soils

RAL-certified potting soils for plants

By offering RAL Quality Assurance for Potting Soils, Gütegemeinschaft Substrate für Pflanzen e.V. has expanded its activities to include another key segment, soils for amateur growers. Consumers often find it hard to judge the quality of potting soils. The RAL quality mark identifies quality soils.

Potting soils are mixtures of the most diverse of suitable constituents, such as peat, clay, bark humus, substrate compost, sand as well as other organic and mineral materials.

The composition depends on the potting soil’s intended purpose. Each constituent has its own task. Potting soils should ensure that the plants are adequately supplied with air, water and minerals at all times. This applies to both indoor plants and outdoor container plants.

What requirements must potting soils meet?

Potting soils must fulfil the following criteria:

  • Provide support to ensure plant stability.
  • Provide space for the roots to grow in and anchor the plant.
  • Supply water and nutrients in just the right amounts and ratios so that the plant will thrive.
  • Have the right soil reaction (pH value) to ensure that the plants can make use of the nutrients.
  • Provide the plant roots with air and water.
  • Be largely free of weed seeds, pathogens and plant-damaging substances.
  • Retain a stable structure even in extremely wet conditions.