The critical role of growing media in modern forestry production

Growing media, or substrates, are soil-free materials designed to support plant roots, provide aeration, moisture, and nutrients

As forestry nurseries adopt advanced container systems, growing media has become key to crop quality and survival - shaping root health, nutrient balance and sustainability from the start

Horticulture

26 March 2026

The production of forestry planting stock has evolved rapidly in recent years, with containerised systems such as trays, paper pots and Growcoon becoming standard across modern nurseries.

These systems offer greater control, improved space efficiency and more uniform crops, but they also place far greater demands on the growing media.

No longer just a rooting substrate, growing media is now a highly engineered component that directly influences root architecture, plant quality and post-planting performance.

At the core of this shift is the need for physical stability. In small cell volumes, even slight imbalances in water and air can have significant consequences.

A high-performing growing medium must retain its structure throughout the production cycle, maintaining an optimal balance between water-holding capacity and air-filled porosity. Too much water leads to oxygen deficiency and root damage, while too little results in drought stress. Equally important is rewetting ability, as some substrates can become hydrophobic once dried, making uniform irrigation difficult.

Nutrient management adds another layer of complexity. Tree species vary widely in their requirements: conifers typically favour acidic conditions, while deciduous species are more tolerant.

Nutrient supply must also be carefully staged. Young plants require low salt levels during propagation, followed by a more targeted supply of nitrogen, phosphorus, potassium and trace elements as they develop. Precision at this stage is essential for producing sturdy, transplant-ready plants.

The increasing use of renewable raw materials such as wood fibres, bark and green compost is further reshaping substrate design. These materials improve aeration and drainage, but they also introduce more dynamic nutrient behaviour, including higher nitrogen demand and increased leaching potential.

As a result, fertilisation strategies must be adapted accordingly. On the positive side, these components can enhance biological activity in the root zone, supporting beneficial organisms, such as mycorrhiza, which are critical for successful establishment in the field.

Manufacturers, such as Klasmann-Deilmann are responding with tailored growing media solutions that combine materials like: GreenFibre wood fibres and TerrAktiv composted bark. These blends are designed to deliver consistent structure, balanced air and water ratios, and stable nutrient availability throughout the crop cycle.

Nurseries report that such substrates are particularly valuable under challenging weather conditions. Improved drainage reduces the risk of waterlogging during prolonged rainfall, while uniform structure supports even crop development. The result is stronger root systems, improved plant resilience and higher survival rates after planting.

As forestry nurseries continue to balance productivity, sustainability and crop security, growing media has become a central lever in production strategy. It is no longer a background input, but a critical factor in delivering consistent, high-quality planting stock.