Which Grodan product should you use?
Every cannabis facility has a different cultivation strategy, from substrate and lighting to CO2, VPD and fertilizers, these differences present a wide variety of growing styles.
Within the Grodan range, there is a wide variety of different rockwool products, including different wool types to different block sizes. These options present solutions for different growing styles or crop requirements.
Choosing rockwool presents significant advantages for the South African commercial grower. Currently 7% of all SAHPRA facilities opt for Grodan and at Hydrobiz, we expect this figure to increase as growers see the advantages of using Grodan
- Reduced labour costs
- Reduced water and fertilizer wastage
- Increased cleanliness and hygiene
- Increased yield and performance
So if you are considering Grodan, lets consider what and how you can use the different products to your advantage.
Greenhouse: These operations are typically large-scale and use natural sunlight, supplemented by artificial lighting and black-our screens to manipulate day length. Not unlike tomato and cucumber production, cannabis cultivation in greenhouses is most often done with Grodan slabs, which have a unique water-holding capacity and uniform nutrient distribution.
Indoor: With indoor cultivation it is much easier to control the environment, and growers can fine-tune temperature, humidity, and light cycles. For growers that have a dedicated vegetative cycle there is the possibility to veg on a 10x10x6.5cm or 10x10x10 block. For Flowering, either a rooted cutting or pre-veg block can be transplanted directly to the larger Jumbo, Hugo, Mama or Unislab.
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
The rockwool used in AO plugs has a lower density compared to Grodan blocks and slabs, which allows young roots from germinating seed or rooted cuttings to penetrate the substrate easily. Hydrobiz stocks the very innovative Smart Tray which allows free drainage and good air circulation to the new roots. Some growers opt to create even more air around the cuttings by arranging the plugs in a checker-board arrangement in the Smart Tray. The AO plug has a dimension 36x36x40mm deep.
Root health is important for nutrient uptake and disease resistance, so monitoring and adjusting environmental factors like humidity and airflow during propagation is critical. Dialing in propagation SOPs can be the difference between an average harvest and an exceptional one.
One Transplant method
The One Transplant method involves moving well-rooted seedlings or cuttings from propagation directly into their final substrate, such as Grodan Hugo or Jumbo Blocks, where they remain until harvest. This method reduces handling and labour and perhaps more suitable for large-scale facilities. Fewer plant movements reduce the risk of pest and disease, as cross contamination during plant movements is eliminated. This method also minimises plant stress but requires careful irrigation and space management.
Consider the Jumbo block at 15x15x10cm with 2.25l for a faster root-in time and optimising canopy height or opt for a higher water buffer for consistent root zone management with the Hugo block at 15x15x14.2cm and 3.2l.
The 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.
Irrigating small plants in large blocks requires precision to manage moisture levels closely, especially in the days following transplantation. Prevent root health issues by overwatering and encourage the small root systems to explore and exploit the whole block.
Two Transplant method
The Two Transplant System involves moving plants twice: from propagation plugs to medium-sized blocks for vegetative growth, and 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 AO plugs to blocks like a 10x10x6.5cm @ 650ml or 10x10x10cm @ 1L. These blocks dry out quickly and this promotes quick root growth, ideal for vegetative root steering. The controlled drying of these blocks is crucial for root oxygenation. The smaller of the two blocks offers a compact option with less buffer, making it suitable for short vegetative cycles, while the 1L provides more volume for longer veg periods.
After the vegetative phase, plants are transferred to larger options such as Uni-Slabs @ 30x20x10cm (6L), Gro-Slabs @ 1mx15x7.5cm (11.25l), or Grodan blocks be it the Jumbo @2.25l, Hugo @ 3.2l or mama @ 4l. The Gro-Slab offers the option to accommodate multiple plants and are ideal for high-density flowering environments.
The Advantage of 2 transplant method is that by using smaller blocks in the vegetative phase you can maximize space efficiency and use a dedicated veg space for veg and after transplanting to a bigger block in the flowering room, you can flip straight to flowering. 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. Smaller blocks dry faster, ideal for early growth stages, while slabs and bigger blocks have a greater moisture buffer during flowering. This flexibility helps to prevent over- or under-watering and reduces the risk of nutrient imbalances.
Delta NG2.0, Improved Wool or MAX
The next question to ask is which wool type should I use.
Delta NG2.0 is the latest generation wool with NG.20 wool technology with easy water absorption and distribution. Delta NG2.0 is part of our retail assortment and suitable for all hydroponic crops from lettuce and tomatoes to cannabis.
Improved wool is what you would typically see on Grodan 101 and the mainstay of the north America market. This product for now is exclusively available to SAHPRA approved licenced facilities. Ideal for mid to High-tech facilities. The wool has an advanced wetting agent that allows for even water distribution and ec throughout the block. Yield can be up to 10% higher in Improved wool than in Delta
Grodan Max Rockwool is the latest generation of Rockwool developed in collaboration with Wageningen University and from extensive research at selected medical facilities. In South Africa, Grodan Max is exclusively available to high-tech SAHPRA approved medical facilities. Like all Grodan products, Max is also made from natural basalt rock, but the brown colour of the wool is because Grodan have developed a new wetting agent and innovative sugar-based binder, and this offers the user to grow in a more ”green” way. Grodan Max wool has optimized properties, with more even water retention capabilities, more even EC distribution and the wool allows a grower to implement precision crop steering through more aggressive drybacks. Compared to improved wool, the superior properties of Grodan max present the opportunity to reduce water and nutrient use by up to 15%, to increase root biomass by up to 10% and increase yields by 5%.
In summary, there is no strict rule to what strategy you opt for but rather look at what your facility limitations and tech advantages are, understand what your goals and objectives are and adapt the strategy to these parameters accordingly. We have growers in SA on a 1 and 2 transplant strategy and we have growers opting for small blocks and slabs at high density and others using 1l blocks at high density. We will be happy to guide you and assist you, whichever way you chose.