Grodan Rockwool Blocks for Cuttings and Seedlings

Consistent Rooting from a Cube That Holds Its Shape

Grodan rockwool blocks are a high-performance, reliable grow media made to deliver strong growth through the propagation phase. Available with a 2.5cm small hole or a 3.6cm large hole, they suit fine seed and small cuttings through to thicker stems. The cube is solid and holds its shape, so it does not slump when saturated. They offer excellent saturation and re-saturation, a positive effect on EC refreshment and distribution, and an excellent air-to-water ratio for rich root growth.

Key Benefits

• Two hole sizes - 2.5cm for seed and fine cuttings, 3.6cm for thicker stems.
• Excellent air-to-water ratio - roots get oxygen as well as moisture.
• Saturation and re-saturation - takes water back up evenly rather than channelling.
• Better EC distribution - fewer hot spots and less salt build-up in the cube.
• Holds its shape - solid, durable and resistant through handling and transplant.
• Strictest quality standards - batch consistency you can plan around.

Slow, Patchy Rooting and Transplant Shock

Cuttings that root at different rates wreck a schedule, and the culprit is usually a substrate that holds too much water or dries unevenly. Waterlogged cubes starve roots of oxygen, giving weak roots and slow growth; dry pockets cause poor nutrient uptake and stalled strike rates. A balanced air-to-water ratio and even re-saturation mean roots develop into a firm plug, so transplant shock is minimal.

How to Use

• Pre-soak: soak the blocks in water adjusted to around pH 5.5 before use.
• Drain: let excess water drain off - never squeeze the blocks, as that ruins the structure.
• Insert: set a seed, or a fresh cutting dipped in rooting gel, into the hole and firm gently.
• Environment: keep the tray in a propagator at around 21-25C, opening the vents gradually.
• Watering: keep the block moist but never saturated - overwatering is the top cause of failed cuttings.
• Transplant: move on once roots show at the sides or base, into a larger block, slab or pot.