What makes a substrate suitable for climate-resilient planting

As growing conditions become more variable across Europe, the specification of a growing media have moved from a routine procurement decision to a strategic one. Unpredictable heat events, shifting precipitation patterns, and increased pressure on water resources all place new demands on the root zone environment. For commercial greenhouse growers, the substrate is not simply a medium for anchoring roots – it is the primary interface between the plant and the climate conditions it must navigate.

Understanding what makes a growing medium genuinely suited to climate-resilient planting requires looking at several interconnected factors: physical structure, chemical stability, raw material composition, and how well the substrate matches the specific crop and cultivation system. Each of these dimensions contributes to how reliably a plant performs when conditions are anything but ideal.

Key physical properties that support climate resilience

The physical architecture of a substrate determines how water and air move through the root zone – and how consistently those conditions are maintained between irrigation events. In climate-exposed greenhouse environments, this buffering function is particularly important.

The most critical physical properties are water-holding capacity (WHC), air-filled porosity (AFP), and structural stability over the full growing cycle. A well-specified substrate holds enough moisture to support the plant between irrigation cycles while retaining sufficient air space to prevent root suffocation. Peat, for example, holds approximately 65% water by volume while maintaining around 30% air-filled porosity – a balance that supports both moisture availability and root oxygenation, as water-efficient growing research from Kekkilä-BVB highlights.

Physical stability matters as much as initial properties. A substrate that decomposes or compacts during a long growing season will progressively lose porosity, restricting aeration and making irrigation management increasingly difficult. For crops grown across multiple months – such as tomatoes or cucumbers – selecting a substrate with proven structural durability is a practical requirement, not a preference.

The growing medium also plays an active role in buffering water availability during heat events or high-evaporation periods, reducing the risk of both drought stress and overwatering. Substrates with well-characterised water-holding properties allow growers to maintain consistent moisture at the root zone while avoiding over-irrigation – a measurable advantage in resource-efficient greenhouse production.

How substrate chemistry affects plant stress tolerance

Physical properties alone do not determine crop performance. The chemical environment within the substrate – particularly pH, electrical conductivity (EC), and cation exchange capacity (CEC) – governs how effectively plants access the nutrients delivered through fertigation, especially when climate conditions place additional stress on the system.

pH is the most immediately consequential chemical parameter. For most greenhouse crops, the target range sits between 5.8 and 6.2. Outside this window, micronutrient availability drops sharply, and plants show deficiency symptoms even when fertiliser inputs appear adequate. In practice, persistent pH instability is one of the clearest signs that a substrate is no longer fit for purpose, a problem that cannot be corrected through irrigation or fertilisation adjustments alone, as outlined in guidance on tailored substrate selection.

CEC – the substrate’s capacity to retain and release positively charged nutrient ions – provides a buffering function that is especially valuable under variable climate conditions. Substrates with higher CEC, such as those containing significant organic matter like peat or coir, reduce the risk of nutrient fluctuations between irrigation events. This buffering effect supports more stable plant nutrition when irrigation timing is disrupted by heat or system constraints.

EC management is equally important. Excessively high EC levels in the root zone induce osmotic stress and nutrient imbalance, while excessively low values lead to deficiency and reduced growth. In soilless greenhouse culture, monitoring total salt concentration in the nutrient solution is the most important chemical discipline a grower can maintain. Substrates certified under the RHP quality mark provide verified assurance on pH, EC, water uptake, and air content, giving growers a reliable baseline from which to manage their crop chemistry.

The role of raw material composition in long-term performance

The raw materials that make up a substrate blend directly determine its physical and chemical performance profile – and how that profile holds up over the duration of a crop cycle. No single raw material delivers every property a professional grower needs, which is why blended substrates remain the standard in commercial greenhouse cultivation.

Peat remains the most widely used raw material in professional growing media, valued for its high porosity, high water-holding capacity, slow decomposition rate, and high cation exchange capacity. Its naturally acidic character and low nutrient content make it highly adjustable: by adding lime and nutrients in controlled quantities, growers and substrate manufacturers can tailor it to meet almost any crop-specific requirement. Peat sourced under the RPP (Responsibly Produced Peat) certification scheme provides additional assurance, as RPP-certified production is restricted to drained and degraded peatlands with a defined after-use plan, excluding high conservation value areas.

Alongside peat, a growing range of alternative raw materials contributes specific performance advantages in blended substrates:

• Coir – a by-product of coconut processing – offers a fibrous texture that resists compaction over time, improving aeration stability across long crop cycles. Its air-filled porosity and hydraulic conductivity make it a useful complement to peat in blends designed for high-drainage requirements.
• Reed canary grass, introduced commercially to European markets by Kekkilä-BVB in 2025, contributes high air capacity and low water retention due to its coarse pore structure. It enhances drainage, supports rooting, and keeps the substrate surface dry, reducing algae and mould formation. Kekkilä-BVB completed its first dedicated reed canary grass production line in Parkano, Finland, in 2026.
• Sphagnum moss (marketed also as BVB Accretio) is a renewable raw material with a harvesting cycle of 20 to 30 years. It combines large water-holding capacity with increased porosity when blended, which accelerates rooting and supports drainage, properties particularly useful for crops with sensitive root systems.
• Miscanthus has been tested as a substrate constituent for nursery shrubs, soft fruits, and growbag cultivation, showing comparable plant yields to mineral substrates in some configurations. It remains an emerging material for professional CEA use.
• Wood fibre is one of the few alternatives that consistently meets professional growers’ performance requirements at scale. Kekkilä-BVB is actively investing in wood fibre supply capacity, with the goal that by 2030 half of the raw materials in its substrate blends will come from sources other than peat.

The practical implication is that raw material selection is not a question of choosing one material over another – it is a question of engineering the right combination for a specific crop, system, and climate context.

Substrate-plant matching for climate-exposed environments

A substrate that performs well under stable greenhouse conditions may not deliver the same results when climate variability increases evapotranspiration rates, disrupts irrigation schedules, or places additional demands on root zone buffering. Matching the substrate to the crop and its growing environment is where the most significant performance gains are made.

Different plant species have markedly different requirements for water availability, aeration, and nutrient buffering. Crops with narrow tolerance ranges – including soft fruits, ornamental plants, medicinal cannabis, young plants, and leafy greens grown in automated systems – benefit most from tailored substrate specifications. For these crops, an off-the-shelf product rarely optimises all relevant variables simultaneously.

For greenhouse vegetables such as tomatoes, cucumbers, and peppers, grow sacks containing limed but unfertilised substrate allow growers to manage nutrition precisely through their own fertigation programmes. This approach gives the grower direct control over the root zone chemistry – an important advantage when heat events or irrigation system constraints require rapid adjustment. BVB Substrates’ propagation substrates for hotter climate zones, for example, use a combination of black and white European peat to engineer higher water-retention capacity specifically suited to high-evaporation conditions.

The substrate specification process should account for greenhouse type, growing system (floating trays, gutters, ebb and flood), irrigation system, local water quality, and the vegetative or generative balance required for a specific variety. When a standard growing medium is visibly limiting crop performance – through poor root zone aeration, inconsistent water distribution, or nutrient uptake problems that cannot be corrected through irrigation or fertilisation adjustments – it is worth evaluating whether a tailored substrate better fits the system. Kekkilä-BVB’s growing media portfolio covers a broad range of crop types and cultivation systems, with substrate composition designed around the specific demands of each.

Sustainable substrate choices that reinforce climate goals

As environmental scrutiny of agricultural inputs increases, growers and substrate suppliers face growing pressure to demonstrate that their material choices are grounded in verifiable evidence rather than general claims. Under EU Directive 2024/825 (Empowering Consumers for the Green Transition), which becomes enforceable across EU member states from September 2026, generic environmental descriptors such as “eco-friendly” or “climate-positive” are prohibited unless substantiated by specific, measurable evidence. This applies to substrate suppliers and growers alike.

The most credible basis for environmental claims in the growing media sector is Life Cycle Assessment (LCA) methodology. Growing Media Europe’s Environmental Footprint Guideline (Version 2.0, published September 2024) provides a harmonised LCA framework for all growing media producers, covering the full cradle-to-grave life cycle. Kekkilä-BVB uses LCA to evaluate the environmental impact of raw materials across extraction, logistics, production, use, and end-of-life stages, providing a factual basis for product development decisions rather than relying on broad descriptive language.

Alongside LCA, certification schemes provide growers with independently verified quality and sourcing assurances. RPP certification confirms that peat has been sourced from drained and degraded peatlands with defined after-use plans. The RHP quality mark verifies that a substrate meets defined standards for water uptake, air content, pH, EC, and phytosanitary cleanliness. These are the types of specific, verifiable credentials that support substantiated claims under the current regulatory framework.

 

This content was generated with the help of AI and it may contain mistakes