Grodan Improved Gro-Slab | 8in - 36in x 8in x 3in

Continuous Stonewool Root Zone for a Block Row, 8in Gro-Slab

Once plants outgrow individual blocks, they need a continuous stonewool volume to root into rather than another single-plant container, particularly in a run of plants sharing one drip line. Grodan Improved Gro-Slab is a 36in-long engineered stonewool slab built on the same hydrophilic fiber technology as Grodan's block line, giving a row of transplanted blocks one shared root zone to grow into.

At 36in x 8in x 3in, this mid-width slab accommodates a row of standard-size blocks without the narrower footprint of the 6in width.

Key Features & Benefits

• 36in-Long Slab — sized to run beneath a row of transplanted blocks sharing one drip line.
• Hydrophilic Fiber Structure — distributes water and air evenly along the slab's length for consistent moisture.
• Individually Bagged — each slab ships in its own bag for handling and placement in a growing channel.
• Chemically Inert Media — leaves pH and nutrient control to the grower's feeding program rather than the media itself.

Who Should Use This 8in Gro-Slab

Growers running a row of standard-size transplanted blocks who need a shared stonewool root zone wider than the narrowest slab option are the fit for the 8in width.

About Grodan

Grodan pioneered stonewool growing in 1969 and, as part of ROCKWOOL Group today, manufactures the Gro-Slab line to the same engineered-fiber standard as its individual Gro-Blocks.

Frequently Asked Questions

What is a Gro-Slab used for?

It's a 36in-long stonewool slab meant to sit beneath a row of transplanted Gro-Blocks, giving them a shared, continuous root zone rather than separate individual containers. That shared volume is common in commercial drip-fed rows.

How do I set up blocks on a Gro-Slab?

Pre-wet the slab with pH-adjusted water, then place rooted blocks on top at even spacing along its length so roots can grow down into the slab. Connect drip irrigation to each block once it's positioned.

Can a Gro-Slab be reused for a second crop?

Most commercial operations run a slab for a single cycle because of pathogen-management concerns in shared irrigation systems. Spent stonewool can be broken up as a drainage amendment or composted afterward.

What determines which slab width I should choose?

Slab width should match how many blocks will sit across it and the spacing your crop needs. A narrower slab suits fewer or smaller blocks, while a wider slab accommodates more blocks per row.