No two commercial cannabis cultivation facilities are identical. Each operation, from layout and lighting to HVAC systems and post-harvest handling, presents its own unique set of characteristics. This variability leads to significant differences in growing styles, media selection, container sizes, and nutrient regimens—especially when considering facilities across the nation. Even when exploring use cases for Grodan stone wool, a leading growing medium for commercial cannabis cultivators, the diversity in cultivation methods remains considerable. This variety stems from Grodan’s extensive product line, which includes blocks of various sizes, slabs, and loose-fill stone wool options, all designed to accommodate different cultivation needs.

One factor remains consistently true for all cannabis cultivation operations: the choice of growing media is fundamental and should be addressed early in the facility design process. The decision to use stone wool, or any other growing medium, impacts critical aspects of cultivation, such as irrigation techniques, runoff management, the timing and duration of different growth phases, and the use of available space. Notably, Grodan substrates have demonstrated significant advantages over traditional media, as evidenced by a recent case study at Medical Saints, a 500,000 square foot greenhouse facility located in Beamsville, Ontario. In this trial, the facility witnessed a 35% increase in yield and a 2-4% increase in cannabinoid content when using Grodan stone wool compared to a coco/peat mix. Additionally, water and nutrient consumption were reduced by 25%, and labour requirements were streamlined due to the ease of using stone wool systems.

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Tailoring Your Selection to Your Facility Type

Facility Types: Greenhouse and Indoor

Cannabis cultivation facilities generally fall into one of two categories: greenhouses or fully indoor farms.

• Greenhouses: These operations are typically large-scale and use natural sunlight, supplemented by artificial lighting to extend day length or boost intensity during the winter months. Due to their exposure to environmental fluctuations, careful climate management is essential. Grodan slabs, which have a unique water-holding capacity and uniform nutrient distribution, are particularly well-suited to these setups.
• Indoor Farms: Indoor facilities offer highly controlled environments, relying exclusively on artificial grow lights. Growers can fine-tune temperature, humidity, and light cycles. These operations often have dedicated zones for propagation, vegetative, and flowering phases, allowing for precise environmental control. Grodan’s improved blocks, such as the GR6.5 (4"x4"x2.5") and GR10 (4"x4"x4"), are ideal for the vegetative stage. Grodan offers several options for onward transplant including larger blocks (Hugo, Big Mama) or slabs (Uni-Slab, GR 6.5 slab). All these options facilitate crop steering techniques  and optimising nutrient uptake, crucial for achieving consistent plant performance at each stage. The ability to control every aspect of the environment means that substrate choice must align perfectly with the facility’s overall cultivation strategy.

Each facility type demands a tailored approach to substrate choice, irrigation strategy, and environmental controls. Understanding how to match your specific conditions with the appropriate Grodan products will significantly influence your operational efficiency and yield quality.

Grodan A-OK Starter Plugs for Propagation

Most commercial cannabis cultivators use cuttings from donor plants for propagation, although stabilized seeds are becoming more popular. Grodan A-OK Starter Plugs are specifically engineered to support rapid and uniform root development in both seedlings and cuttings; their lower density compared to Grodan blocks and slabs allows young roots to penetrate the substrate easily, establishing a healthy root system early on.

Size Options for A-OK Plugs:

• 1” A-OK Plugs: Ideal for high-density seedling trays or compact propagation areas. They are often arranged in a chequerboard pattern to promote air circulation and minimise the risk of fungal diseases.
• 1.5” A-OK Plugs: A larger option providing more volume for robust root growth and better moisture buffering. Suitable for growers who need more time in the propagation phase before transplanting. These plugs also reduce the frequency of irrigation events, helping to manage moisture levels more effectively.
• 2” A-OK Plugs: The largest A-OK option, providing a slightly larger root environment for robust seedlings or clones before transplanting. These larger plugs provide an ideal root environment for plants that need longer propagation times before moving into vegetative growth.

Proper selection of A-OK Plugs ensures a strong start for your plants, setting the stage for success in later growth stages. Root health is foundational for nutrient uptake and disease resistance, so monitoring and adjusting environmental factors like humidity and airflow during propagation are critical. Dialing in propagation SOPs can be the difference between an average harvest and an exceptional one, making these early decisions critical.

One Transplant System

The One Transplant System involves moving seedlings or cuttings from propagation plugs directly into their final substrate, such as Grodan Hugo or Jumbo Blocks, where they remain until harvest. This method reduces labour and minimises plant stress but requires careful irrigation and space management.

Advantages:

1. Labour Efficiency: Simplifying handling and eliminating the need for an intermediate transplant significantly reduces labour, which is a key advantage for large-scale facilities. The streamlined process allows cultivation teams to allocate resources to other critical areas, such as monitoring plant health and optimising environmental controls.
2. Pest Management: Fewer plant movements reduce the risk of pest infestations, as plants remain in their designated grow areas throughout their lifecycle. By limiting plant movement, the risk of cross-contamination is also minimised.
3. Consistent Root Environment: Final-stage blocks like the Hugo and Jumbo provide a stable root environment, facilitating uniform nutrient and water uptake. The Hugo Block (6"x6"x6") offers a high moisture buffer making it ideal for consistent root zone management. The Jumbo Block (6"x6"x4") has a lower substrate volume, providing a faster root-in time and optimising canopy height in vertical grows.

Additional Considerations:

1. Space Efficiency: Early-stage plants will occupy significant space in their final locations so grow light intensity and photoperiod will need to be adjusted accordingly. Plants will need to spend some extra time in vegetative growth before being flipped to flower in the same location. Careful planning is essential.
2. Moisture Management: Irrigating small plants in large blocks requires precision to encourage small root systems to explore and exploit the whole block. Grodan’s GroSens sensors provide real-time data on water content, enabling growers to adjust irrigation schedules and avoid root rot or nutrient lockout.

Growers using the One Transplant System should monitor moisture levels closely, especially in the days following transplantation, to ensure optimal plant health.

Two Transplant System

The Two Transplant System involves moving plants twice: from propagation plugs to medium-sized blocks for vegetative growth, then to slabs or larger blocks for flowering. This approach maximises space efficiency and supports root development but requires meticulous timing and additional labour.

First Transplant: Young plants are moved from A-OK plugs to blocks like GR6.5 (4"x4"x2.5") or GR10 (4"x4"x4"). These blocks promote rapid root growth while drying out quickly, ideal for vegetative root steering. The controlled drying of these blocks is crucial for root oxygenation. The GR6.5 block offers a compact option with less buffer, making it suitable for short vegetative cycles, while the GR10 provides more volume for longer growth periods.

Second Transplant: After the vegetative phase, plants are transferred to larger substrates such as Grodan Uni-Slabs, Gro-Slabs, or Grodan Uni-Blocks. The Uni-Block (8"x8"x4") offers a substantial 4.0 L volume, supporting larger plants and providing flexibility for both greenhouse and indoor operations. It serves as an intermediate substrate, ideal for environments that require a balance between moisture retention and aeration. The Uni-Slab (8"x4"x9.5") offers 11.3 L of substrate, perfect for single-plant setups needing stability and moisture buffering. Gro-Slabs, available in widths of 6", 8", and 12", can accommodate multiple plants and are ideal for high-density flowering environments.

Advantages:

1. Optimised Space Usage: Using smaller blocks in the vegetative phase maximises efficiency, while larger substrates support plants as they mature and transition into flowering.
2. Enhanced Root Steering: The staged transplanting allows for precise root zone management to promote either vegetative or generative growth. Growers can tailor irrigation strategies to achieve desired outcomes, such as faster vegetative growth or denser flowering. Root steering practices should be regularly adjusted based on environmental feedback and plant health observations.
3. Flexible Irrigation: Smaller blocks dry faster, ideal for early growth stages, while slabs and Uni-Blocks offer a greater moisture buffer during flowering. This flexibility helps to prevent over- or under-watering and reduces the risk of nutrient imbalances.
4. Dense Root Colonisation: Starting with smaller blocks ensures a well-developed root system before the second transplant. This promotes efficient nutrient and water uptake, laying the groundwork for a productive flowering stage.

Selecting the optimal Grodan products for your cultivation facility involves a comprehensive understanding of various influencing factors. These include your chosen propagation method, specific strain characteristics, lighting technologies and setup, expected final plant size, and physical constraints such as ceiling height.

Grodan offers robust technical support to ease your transition to stone wool and optimize results. From initial setup to ongoing cultivation, Grodan’s team provides personalized guidance tailored to your facility’s needs. This includes advising on substrate selection, irrigation strategies, and environmental controls.

Ready to dial in your substrate strategy?